Guess it could depend on the specific material, but I've used it recently on my Tamiya S2000 body with no problems. You need to leave the part immersed for several days though (depending on how old the paint is). Then wash it with neat detergent, then wash and rinse in hot water.
There used to be a product called Modelstrip which was specifically intended for removing paint from plastic, but I don't know if it's still available. Someone I know says Mr Muscle Oven Cleaner will do the same thing!
I've used Model Strip a couple of times and it definitely works. However, it is extremely bad value for money as, over time, it goes hard in the tub. You end up only using about 1/3 of the tub.
