The idea of developing Trainz for Mac unfortunately faded away, don't think it has ever been officially announced as dead. Went the same way as Rail Sim Pro, I guess, easier to keep developing hyped up versions of TRS2004, which in itself is really a development of the original Trainz. It seems these kind of things are announced to be made but when the decision is made to dump them nothing is said, maybe in the hope that people will just forget about them.