Only one can win. Two theories from the Washington Post:
If the bonuses weren't paid, the AIG staffers would be able to sue the company and probably would win, not just what they were owed but also punitive damages that would make the ultimate cost perhaps two to three times as high as the bonuses themselves.
Jonathan Macey, a professor at Yale Law School, said it was unlikely that any AIG employees would end up suing the company for changing compensation contracts, mainly because their names would be revealed publicly in a lawsuit and they would then be excoriated.
On the other hand, it seems entirely possible that the names of the relevant AIG employees will come out anyway.