Does anyone have any insight on exactly what this new rule - ostensibly to prevent "collisions at home plate" - would mean?

News reports have been pretty vague and somewhat contradictory. Some state that the runner "couldn't plow into the catcher", others talk about how "the catcher couldn't block the plate"...

I've always believed that the catcher, if he blocks the plate before he has the ball, is as guilty of fielder's interference as a 2B, 3B or any other defensive player. On the other side, a runner going into home shouldn't be able to do anything to a catcher that he couldn't do to a defensive player at 1B, 2B or anywhere else, i.e. no reaching out and shoving with his hands; that shouldn't be legal, either.

How do you guys understand the pertinent rules now, and what's the deal with the proposed changes?