Different instructors have different philosophies. The minimum agency standards, and what many teach, is pretty much an OC cave class where you happen to be wearing a rebreather. Personally, I think CCR cave should be about using the rebreather to extend range (otherwise what is the point), so a class will involve 3-4 hour+ dives and some problem solving a long way back in the cave. We provide CCR cylinders and sorb, so have a lot of rebreather divers diving out of our centre in Tulum and absolutely require a CCR Cave certification. Given the variable standard of training out there, I would be very uncomfortable with enabling a diver with Mod 1 and OC Cave to dive in the fragile and complex caves in Mexico.