I tested it out the 1000Lb numbers failed to drop a bridge more than half the time. and alot of the time it seemed to bounce off buildings. Granted this was in the DOS game. I shall try it in WinMBT shortly.
I did try an experiment of replacing the 1000Lb bomb unit with a FASCAM, just to see if it would work... It didn't
One other problem you might want to look at is, units with crew 0 die automatically on the first turn, not when they renforce.