I wouldn't trust this post either. Now that the ASP and .net junkies can reach in and do stuff via the CLR, it's anybody's guess. And it is still so vexing that MS did not see fit to add attributes like "last modified" and "last accessed" in SS 2005 - Windows has had that capability for a long time.

AFAIK the only sure way to track when an sp is invoked would be to add tracking code e.g. write to a table when it is executed.