The Federal government absolutely would not mandate a monopoly over the country for safety concerns. The vehicles are already licensed on a per-state basis and it stands to reason that states or cities, who already regulate taxis, would extend that power to autonomous taxis.
Which means, if SF gives a monopoly to Google, then LA might give one to Mercedes, while NYC gives one to Ford. (Or whatever). The point being, there is still competition overall to win the business of municipalities.
That's the same argument that allows Comcast to be the only ISP in my area. There's no competition within my area that allows me to make a conscious decision to reject a company.
If my municipality is making the decision, then there is a politician who can be bribed into keeping that utility into place. Really, a terribly system.
