Aha! It's old, but I found a list of some corridors where rail was reinstated, at least in part, so the question "has any railbanked/rail-trail corridor ever gone back to rail" can be answered "yes." Notice that it's almost always "in part" and usually a very small part.

[www.americantrails.org]

Also, the court actions noted in the original post are in the Court of Federal Claims. That's where you go to be compensated if an action of the Federal Government (in this case, the Trails Act and related STB decisions on public use) affects you or your property. You make a claim by filing suit, and if proven you get paid. That has nothing to do with the legality of the program (rails-to-trails has been found legal in other actions), only the cost. And some Federal agency (presumably somebody in DOT?) is the one responsible to pay. Basically implements the Constitution: taking of private property for public use has to be compensated for in some way (usually with dollars).