If the cars that fall back to AI then communicate their observations and decisions back to Google then to other cars then the next car wouldn't need AI and could improve knowledge of the area, plus any particularly bad problem spots can be highlighted for further investigation at Google HQ.
Personally, I think that's a brilliant idea. Some how I don't think the privacy rights crowd is going to be thrilled it though. The "Evilz Big Corporation" will be able to take over the world, control your mind and force you to buy figgy pudding. The only thing stopping them now is not knowing where you are physically located.