That's a very good question.
I would have to say this. The auto companies generally see the powertrain as a core technology that is part of their competitive edge. So they don't collaborate too much on engine technology per se, but they're doing a lot on transmissions and hybrid drive systems.
One of the most interesting and quite surprising partnerships is actually between General Motors, Chrysler, BMW, and Mercedes. They're developing what's called a two-mode hybrid transmission for rear-wheel-drive vehicles. I believe the R and D centre for that is in Troy, Michigan, and it actually has four separate sections, one for each of the companies. There are common areas where they meet and try things and talk, and other areas where it's verboten for the other guys to go.