Speaking in a recreational context, yes.
The only people who are (generally) adopting a standardised gas share protocol for mixed teams are the DIR agencies.
As far as Type-R CCR diving is concerned
...
If on the other hand, you are diving with Type-T rebreather divers
Given the forum we're in, using the terms Type-R and Type-T without defining them might not be sufficient for some readers.
Also, it's worth noting that serious technical CCR divers can still be found on ordinary, recreational dive boats. So, you can't really infer what kind of CCR diver they are strictly by the boat you're on. Nor, necessarily, by looking at them, either.
I think, from a recreational, OC diver's perspective, the best bet is, if your buddy is a CCR diver, have a pre-dive chat to cover emergency procedures and OOA protocols. If you can't, don't buddy with them. If they can't give you gas, don't buddy with them. If it's simply a CCR diver on your boat, still try and have a chat with them. If you can't or don't, then assume they are not a source of gas for you in an OOA scenario.
And, be smart. Don't go OOA. Be a good buddy. If you have a failure that causes you to lose your gas, get gas from your buddy - not a random CCR diver you happen to see.
I dive OC with a CCR buddy. I know how to turn his BOV to OC, if I need to. Otherwise, we gear up and plan our (recreational) dives as if we're each going solo. I have my own redundant gas and he has his own. I have never given much thought to how I would get gas from him, but this thread has given me pause to think. Not so much for concern for myself, but I'm going to ask him about how he would handle it if we were on a recreational boat and some other diver came to him in an OOA panic.