Is there anybody around here who understands the nif animation stuff? Or can give me a pointer?

Touring Carriages uses the vanilla passenger files. But they have their hands tied (because they are prisoners). Even the vanilla scripts have comments about needing replacements. Both Real and Scenic Carriages have extra code to try to untie the hands, unsuccessfully.

IdleCartPrisonerAExit gets them off the cart

IdleCartPrisonerASway puts them on the cart

etc.