Yes, KISS. I want just enough info to help me or my CCR buddy if either of us gets into trouble. I don't want a short course on CCR's. I have too much else to think about. I agree with Doctormike that it's on the CCR diver to explain his equipment to the OC buddy. I also agree with Stuartv that the responsibility should lie with the OC buddy to ask the pre-dive questions of the CCR buddy after her pre-dive check. The assumption is that the CCR diver knows OC but the OC diver doesn't know the CCR equipment and it is in his best interest to ask the pertinent questions. Regardless of who initiates the discussion this really isn't any different than a pre-dive briefing between a pair of OC buddies where each buddy explains the location and use of alternate air, weight release, etc.
bowlofpetunias brought up an interesting issue regarding DM led group dives with CCR divers. My own thinking on this is if most of the divers are OC than I'll ignore the CCR diver and stay close to an OC diver in case of OOA emergencies. If most of the divers in the group are CCR than I'll make it a point to buddy up with a particular CCR diver and ask about air sharing and other issues. Hopefully, dive charters will be conscious of these scenarios and insist on pre-dive briefings that include sharing information with and from CCR divers.