What does the law say? It isn't listed as off limits. Do motor vehicle laws apply? Its very spacious inside. Like a big moving room.
Smart is private company yes? If they are, then I think they have the ability to make the rules, and you're bound by them. However, if Smart is public transportation, I would think it would be covered by preemption. Also, though, CPL laws are MI laws and therefore on the same ground as preemption, so they still apply, any carry on/in a vehicle is considered CC and a CPL is necessary, private or public.