So far, sounds like a boondoggle. Shocking. Fares for tourists are reportedly 6x what locals pay and taxi fares to the hubs from tourist areas are really expensive. I've not taken it. Just from what I read on a FB page for Riviera Maya news.
https://www.rivieramayanews.mx/maya-...-figures-show/

From this booking site, it looks like international tourist costs are double the local tourist cost; there's an in between cost for nonlocal Mexican nationals plus a lower fare for students, teachers, seniors, and individuals with disabilities who are Mexican nationals. I put in a sample and it's ~$26 from CUN to Tulum. I'll be interested to hear if anyone on here has tried it.
https://reservas.ventaboletostrenmay...b/booking/home

I'd pay $26 to get from CUN airport to Tulum.

Belize is in talks to have the train extend a line there from the Mexican border city of Chetumal. That could be a long time off.