Your description is a little confusing. "Level, animations and Tootie are not a part of this mission." What do you mean by that? Because the only thing that's out of place is the NPC's and the opening dialogue. And Tootie is apart of that mission.
Or are you talking about the actual Trainspooking level?
Audio(From unusual suspects), team selection menu and scripts are from the original mission. There are three ghost busters what are hidden until you not solve the puzzle. Tootie was added there just for make this level playable(otherwise plasm is set to 0 what means instant game over).