Sony has it's finger in so many pies they could collaborate anywhere. Negotiate as a computer company, phone company, music distributor, movie company, game console company, game writer company, stereo-system company, etc
Much as I'd like it, I don't see Apple licensing Mac OSX. I think they'd have to charge a high amount to reflect their cost of upkeep, and Sony wouldn't pay it.
I could see potential for Apple to license iLife-for-Windows to Sony though. It would give Sony a nice differentiating factor, incorporate iTMS, give Apple some iLife revenue, and extend AAC support. And open up many more possibilities.
(would the HP deal prevent this?)