@stuartv sounds like you and your buddy are well versed with each other's gear which is great. My concern is that other ow divers know to ask the questions if their ccr buddy isn't forth coming about things. Also I am concerned about the potential at our local dive sites where we see CCR divers fairly regularly on shallow dives where new and inexperienced divers are diving. The CCR divers are there taking advantage of the no bubbles to do photography.
That is why I put this question in Basic
Right. My real point is that I kind of agree with those who have said that they don't agree with trying to teach CCR basics in an OW class. It's too complicated. Thus why I was suggesting a simple approach that is pretty much the same thing you'd do with any buddy, CCR or OC.
Have a pre-dive talk and go over emergency stuff, including OOA. If you buddy can't donate you gas, then don't buddy with that person. If they won't explain how you should deal with them, don't buddy with them. All true whether your buddy is OC or CCR.
Try to have a chat with any other CCR divers on your boat.
Bottom line: If you see a CCR diver in the water, unless you have had a pre-dive conversation with them to the contrary, assume (i.e. conduct your dive as if) they are not going to be able to help you if you go OOA.
From what my regular CCR buddy has told me about other CCR divers he has been in class with, I wouldn't have much confidence in swimming up to a CCR diver and asking for gas and having them respond in a useful way, anyway. How much CCR training goes on where the CCR diver is specifically trained on responding to other divers who are OOA? I'm sure the good instructors cover it. But, I'm not sure they ALL do. At least with a random OC diver, they are almost certainly going to have an alternate air supply on them. And if they don't, they CAN share the one they are using, if they have to (and are willing and don't panic themselves).