Learn English – What’s the best way to use “either” on more than two options?

I like Jimi Oke's shortest suggestion, but I will also add one further minor tweak:

The weight of services given by Company B is no less than that of Company A.

"No less than" is a better idiom for expressing "at least equal to".

First of all, it's common usage, that is, in native English speech, to refer to multiple choices using either, but it's not entirely grammatical (from a prescriptivist's point of view). The definition of either is:

Each of two. [from 9th c.]  
One or the other of two. [from 14th c.]  

Note that I say it's common in informal speech and usage, but probably not for formal contexts.

An entire page of Wikipedia was devoted to this word, and the definition given was:

Either/or means "one or the other." Its usage, versus the simple or structure, is often for emphatic purposes, sometimes intending to emphasize that only one option is possible, or to emphasize that there are only two options.

Thus, it depends on what the context is. If in speech, then either would be appropriate. If however, in a formal context (business letter, etc.), then using either for multiple choices would be inappropriate.