"...pagination is done after the transformation, in an independent step.
Therefore there is no way to get hold of the number of prescriptions
laid out on a certain page in the transformation.  The layout process
itself lacks higher level functionality like counting, so no easy
solution here either."

Is this still true?  Is there no way to access nodes by page (for
instance, from a footer template) without forcing page breaks?

That's correct. Some FO processors have extension functions which
might allow to do certain things.