It depends on whether or not he was dismissed "for cause." I don't have the specifics on Condit's contract, but a lot of them are structured so that if the exec is dismissed for cause, they get nothing. Of course, for cause often is so loosely defined that even Kozlowski at Tyco still got a sweet severance, despite being charged with fraud!
Catch there is whether a guy was actually "dismissed" or if he resigned before the Board could convene to send him packing. If the CEO resigns, he probably keeps his GP even though he was up to no good. If the Board tried to vote out his severance after he quit they'd probably find themselves sued.
I have no idea if this happened in the Tyco case but it is an easy scenario to envision.