I haven't tried this, (and you'd never have a need to) but I think they are incompatible. The reason you'd never have a need to is that if you had a set of T/A taillights with good covers, then the rest of the lamp is going to be good too. Taillights are the least rare part of a car.
The reason I think they're incompatible is that Trans Am taillights have a nice bright and shiny red taillight under the smoked cover, and they need that. Firebird taillights don't need that and as far as I know, it's not in there. I've never taken the cover off a firebird taillight.
They also have different numbers of bulbs, but anybody with an ounce of sense would be fine with that.