collective-nounsgrammatical-numbergrammaticalityverb-agreement
I'd say Microsoft have a way of bending the rules and I know that McLaren have won the championship. While this sounds strange, I believe it is correct English (sorry, I'm not native).
But when it's a small company, would you still use it this way? Is a company always plural, or are small companies singular? I.e., would you say Bakery Johnson makes fine bread or Bakery Johnson make fine bread? Is it My book seller, Woody's, have moved or is it has moved?
This may be the copy editor in me speaking, but I think your first step should be to decide whether you intend to talk about "the company" as a collection of human beings performing various tasks or as a monolithic entity taking actions in a monolithic way. In U.S. English, in my experience, people tend to treat a company as a (singular) thing, not as a (plural) multiplicity or agglomeration.
In the OP's presentation, the sentence in question associates "Company X" with two activities: (1) expanding and (2) hiring a new CEO. To me, it doesn't seem especially accurate to say
The people of Company X are expanding and are hiring Person Y as their new CEO.
True, the people at Company X may benefit from the company's expansion and may become more numerous, but focusing entirely on the headcount sense in which they are indeed expanding seems a bit arbitrary, given that the company as an entity is expanding in many other ways as well (including revenues, markets, contractual agreements, and physical plant); and very few people at Company X are likely to have any say in the hiring of the new CEO. It therefore seems either that "Company X" is being referred to in its monolithic sense with regard to both activities (1) and (2), or that it is being referred to in its monolithic sense with regard to activity (1) and as a convenient shorthand for "a handful of top executives" with regard to activity (2).
To my mind, it is simpler to stick with the singular understanding of "Company X" throughout:
Company X is expanding and is hiring [or has hired] Person Y as its new CEO.
than to try to convey the mixed understanding at midstream:
Company X is expanding and [members of the CEO search committee] are hiring [or have hired] Person Y as their [and every other employee's] new CEO.
As for the argument that the singular form of they may be implied at the crossover point:
Company X is expanding and [they, understood singularly] are hiring [or have hired] Person Y as their [understood singularly] new CEO.
it seems to me that they has not been widely adopted (in the United States, at least) as a gender-nonspecific singular pronoun replacement for the gender-nonspecific singular pronoun it. I discuss this question on the other side of the gray rule below. On this side of the rule, I shall wrap up by observing that the sentence "Company X is expanding and is hiring [or has hired] Person Y as its new CEO" is formally consistent and practically unambiguous, whereas the sentence "Company X is expanding and are hiring [or have hired] Person Y as their new CEO" is formally inconsistent and a bit startling to read, and requires some effort by the reader to work out its logical underpinnings. For those reasons, I strongly recommend using the wording "Company X is expanding and is hiring [or has hired] Person Y as its new CEO."
Some thoughts about 'they' as a replacement for 'it'
To me, the most interesting thing about this question is the secondary question it obliquely raises about the suitability of replacing the gender-neutral singular pronoun it with the repurposed gender-neutral plural pronoun they.
The original argument in favor of using they/them as a singular pronoun, I believe, was that it avoided the gender specificity of he/she/him/her, and that the resulting gender neutrality justified what many people felt (during the period of transition to its widespread use) was a rather clunky-sounding application of a plural pronoun to singular duty. We have now emerged at the other end of that tunnel, and many people don't think twice about using they/them in place of a gender-specific singular pronoun.
But what does that mean for the future of it as a singular gender-neutral pronoun? Are people who have grown up using they as a gender-neutral replacement for singular he/she likely to use it also in place of singular it? Here is an Ngram chart for the years 1700–2005, tracking the frequency of use of it (blue line) versus they (red line) versus them (green line):
As you can see, the frequency of all three pronouns has tailed off a bit in the past 200 years or so, but there is no sign that the dropoff in usage of it has contributed to a gain in usage of they/them. The probable reason for this, I hypothesize, is that there has been virtually no tendency among people writing in English to replace singular it with singular they/them; and I would be quite surprised if the same were not true of people speaking in English.
The most notable exception to this general trend is precisely in connection with news reports about companies and other personifiable entities: Like the U.S. Supreme Court, Americans have a tendency to anthropomorphize individual businesses as, in some sense, thinking beings with a hierarchy of values, a viewpoint on social issues, and a political as well as commercial agenda. But even though it is not uncommon to see "a company" discussed in terms of "their" latest actions (especially where individual actors within the company are implied and sometimes even visible), it remains very rare to encounter a news report in which a company is first identified as "it" and then summarily shifted from that pronoun to "they."
Fundamentally, there is no good reason to replace it with they/them: Doing so doesn't make the language less biased, and it certainly doesn't make it clearer. So I suspect that it will carry on not much affected by the revolution in use of they/them in place of he/she/him/her.
Yes, there are plural abstract nouns. Here are a couple (emphasis, mine ... come to think of it, emphases is also a plural abstract noun):
state noun 1 The particular condition that someone or something is in at a specific time. ‘the state of the company's finances’ - ODO
stage noun A point, period, or step in a process or development. ‘there is no need at this stage to give explicit details’ - ODO
From the list of nouns you were "in no way asking about", deserts, earnings, odds, damages and condolences are plural and abstract. Brains and guts are metonyms of concrete plural nouns.
What makes an abstract idea countable is the same as what makes a concrete noun countable: an accepted boundary to its extent. A pool (of water) can be distinguished from an adjacent pool because it has finite dimensions (you can tell where one pool finishes and where another starts). Likewise, there's a logical extent to ideas, states and stages, etc: you can tell where one of those finishes and another starts. On the other hand, the extent of air, water and flexibility is, in each case, somewhat nebulous, so they are treated as mass nouns. They can be quantised, however, and it's typically the quanta that are counted - e.g. a puff of air, a tract of water, a point of flexibility. Sometimes, the mass noun is used as a metonym for the quantum (e.g. in restaurants: 'one water' for 'one glass of water'), but this is straying outside the bounds of your question.
The issue with abstract nouns may be that extent is a conceptual matter there. One can't take a ruler to it or build a box to contain it. Nevertheless, if the abstract noun does have an (abstract) extent, it is countable.
Best Answer
american-english
These company names are collective nouns. In general, in American English collective nouns almost always trigger singular verb agreement (after all, "Microsoft" is grammatically a singular noun, even if semantically it denotes an entity made up of many people). It is apparently much more common to use plural verb agreement in British English. It doesn't have anything to do with the size of the company.
Lots of good information here: Language Log on collective nouns, etc.