Answering the topic question - no, there is no proof of radical changes of already established physique. And not only calves or forearms, but everything else too.
If individual is juiced to the gills and has any serious flaw, there is no way how he can completely fix it (not talking about synthol-like compounds now).
You can check various theories on muscle growth (most about that muscle cells number is predetermined, only their size can change) and it will become apparent that there is nothing you can do with lagging muscle if you already train it, use gear and that doesn't work. All the possible changes are minor, but sometimes they are enough to make weak bodypart more visually pleasing (i.e fuller) and kinda improve overall look.
Theories aside, example from real life - below is a bb who (often said) improved a lot.
But does he really changed that much for almost ten years of juicing and training?
The same goes with Heath, Wolf, etc. To me they look almost identical every year since their first Olympia.
