I can imagine it for the sake of argument, but without strong govt action it has a bootstrap problem: no one will create such a lane if there are no such cars,

I can imagine it for the sake of argument, but without strong govt action it has a bootstrap problem: no one will create such a lane if there are no such cars, and no one will buy and develop them if there are no roads you can use them on. Moreover, if the goal is to achieve autonomy with relatively dumb algorithms that fall short of full self driving, you have to do grade separation, fencing, tunnels or overground etc., otherwise you still need full self driving to handle those case where bikes or children roam around in your "dedicated" lane, cars and garbage bins are parked on it, drunk drivers suddenly invade it etc. And if you go the full trouble of dedicated and grade separated infrastructure, why not build a tramway or PRT (like the Booring Co Loop system) that any citizen can benefit from? All in all, I can't see the scenario you are describing happening in any real city with real politics, maybe some oil prince can decree it.