My personal theory is that transportation is going to become more and more customized and tailored as the years and the technology progresses. In a sense, Google could use the same strategy with their self-driving car as they can with Android. Build a proprietary software platform, license it to hardware manufacturers and let others come up with services to use it (apps). Imagine not owning a car, but instead summoning a car on an as-needs basis. The company who owns the car can offer you a range of cars from small hatchbacks to SUV's. It's similar to regular car rental but could be much more granular. If you really want the comfort of a Mercedes over a simple Chrysler, you can just pay more. Or if you want a red car. Or a car with [insert preference here]. Whatever company owns the car can retrofit some sensors and get it out on the road. Your scenario of pay-to-be-faster depends on whether fully automated cars will be so-called 'connected cars' or not. Will they talk to each other? Car companies are really pushing for connected cars, partly because they produce so much data. But fully automated cars can totally work without being connected. There's added benefits like the ones you described, but connecting all cars to each other could be an insurmountable challenge, or just not worth the added cost.
Google is going to lease their dataset and bundle a precertified constellation of sensors and servos as a VAR. They're going to be Delphi. Their contracts are going to require two way communications such that Google gets to retread and revise their master database everywhere their cars travel. The Google-Car-As-Uber discussion is wholly separate; the actual hardware won't be any different, just the ownership. Zipcars are well-established and legally uninteresting and I can totally see Google operating a vast fleet of autonomous vehicles at a loss in order to increase the penetration and acceptance of their offerings in order to drive B2B sales. Come to think of it, that's a good reason to short sell Uber and Lyft - there isn't a single market that has survived once Google decides to enter it. Google has a solid and logical reason to get into car hire and they will beat Uber and Lyft by inspection. And I think Google could structure their services in such a way that they couldn't be barred from use at airports the way Uber and Lyft are... there might be an in using membership modeling that would make them livery rather than for-hire. But that's well beyond my expertise.