Re: Insurance
"Do you really think some beneficent organisation is going to invest in a vast fleet that gets used a few times a day at rush hour & then stays idle?"
They already do. They're called 'taxi companies'. Presently they have drivers, who are the really expensive bit. Without them, it's much cheaper - and they don't need to stay idle outside of rush hour. Many companies would benefit a great deal from being able to ferry staff and goods around on the cheap during the day, without having to keep their own fleet of vehicles; being able to take non-driving expert staff places for a low subscription cost would be a more or less automatic purchase in the same way that Exchange 365 is becoming how email is done in the enterprise.
Think in terms of scale. If you're running a self-driving car sub service for Manhatten, you have a potential customer base of 7 million people and a couple of hundred thousand businesses. That's a yearly turnover of half a billion. You can pretty much afford to have tens of thousands of cars at that price. Sure, maybe you'll have some car pooling at peak times; that's not a bad thing and reduces congestion all round.
Either way, if you can offer car access when required for cheaper than the running costs of having a non-self-driving car, it's not an outlandish idea.