SHORT ANSWER:
Yes, the continuative present perfect may be used to signify a state which continues right up to the present regardless of whether it continues in the present. It is not, however, used to signify a state which does not continue right up to the present.
LONG ANSWER:
The 'continuative' present perfect establishes the past event or events it names as a state which endures right up to the present.
Situations grammatically depicted as states are presumed to continue indefinitely, until something happens to end them.
Consequently, the present perfect permits you to infer that the state it describes continues in the present. In fact, this is the default assumption with an unqualified present perfect. If you had only the statement “I've been driving a hearse for the last 25 years” you would legitimately infer that he is still driving a hearse.
But the present perfect does not entail—logically require—the continuation. Linguists call this an implicature, as opposed to an implication: it is in inference which may be cancelled by a contrary fact. That's what you have here, with the statement “Today is my first day driving a cab.”
Note, by the way, that there is in this particular use of the perfect, no difference between the use with the progressive, “I have been driving”, and without it, “I have driven”. The phrase “for the last 25 years” imposes the same continuative reading on both.
Note, too, that because the hearse-driving does not continue into the present the speaker might with propriety have employed the ‘simple past’: “I drove a hearse for 25 years.” I suspect he uses the perfect (and the progressive) because what he wants to convey is that there is a continuity in his activity: “I’m still driving, what’s changed is that now I’m driving a cab.”
Note, finally, that the notion of ‘present’ is defined pragmatically. Obviously when someone says he has driven a hearse for 25 years he does not mean that he drove continuously throughout that period. By the same token, the ‘present’ which that driving continued ‘right up to’ is not the moment in time when the statement is uttered but “today”
The case of John’s tardiness is a little different. In the circumstances you describe, neither the continuative present perfect nor the phrase “for the last 30 minutes” is proper. You are dealing with a much different timeframe and scale than the cabdriver. Your answer (“alas”) makes it clear that you are pragmatically defining three distinct epochs: 1) you wait for 30 minutes 2) you depart, and a couple of minutes elapse—long enough, at any rate, that you are no longer in the vicinity of the appointed meetingplace 3) then John calls. Consequently, the state of waiting (1) did not continue “right up to” the present (3).
Here are some ways you might express the facts:
I waited for you for thirty minutes, but, alas, when you didn’t show up I left.
I waited for you for thirty minutes, but, alas, I’ve left now.
I waited for you for thirty minutes, but, alas, I had to leave.
You should not employ the progressive I was waiting here; that is employed to speak about something which happened while you were waiting.
I agree with you: What are you going to do this evening? is just as acceptable and ordinary way of asking this question as What are you doing this evening?
Within the given parameters, so are:
What will you be doing this evening?
What are you going to be doing this evening?
Even this, which is ordinarily a very stilted way of expressing it, may be appropriate and natural in some circumstances:
What will you do this evening?
But this doesn’t necessarily mean that the book is wrong; it may be that something in the instructions excludes constructions with BE going to from consideration in this particular question.
Best Answer
The present continuous, and not the simple present, is called for in both of these sentences.
We use the present continuous (or present progressive) to talk about events or conditions that are in progress or unfinished at the time of speaking. We use the simple present to talk about events or conditions that take place in general.
When we say "It rains", we say only that rain falls, without any reference to the time of the event. When we say "It is raining", we say that the rain falls as we speak.
Thus, the present continuous is correct in your first sentence:
It is sensible to take the umbrella if the rain is in progress at the time of speaking. If the undeniable fact that "it rains" were a plausible reason to carry an umbrella, everyone would carry an umbrella every moment of every day!
In your second sentence, the same principle applies. When we say "You wait", we say only that the subject waits, without any reference to time. When we say "You are waiting" (or, with subject–auxiliary inversion in the interrogative form, "Are you waiting"), we say that the person waits at the moment when we speak.
Thus, the present continuous is also correct in your second sentence: