I cannot give an answer but I attended a webinar from Moscow embassy on various questions. On a different type of visa (I think student but don't recall) they said they would mostly be automatically extending the validity of medical exams, and in some other cases not automatically extending but 'expected' to extend the validity.
So I think there is some hope - at this point only a hope - that they will have a bias to extending the validity of medical exams, particularly if only for a few months.
I think this makes quite a lot of sense and particularly for family class, where the purpose of the medical exam is more limited (mainly dangers to Canadians i.e. communicable diseases) and not about cost of medical care. They are also aware that the processing is not cost-free for government either.
Again, no guarantees and this may not apply at all for cases where medical results are much more out of date. (And as this drags on the results will only get more out of date)