That's a major benefit to rolling this out as a cab company rather than as a car manufacturer - you can enforce limits like that and people won't complain because they won't even know about the 98% of roads you haven't automated yet. Assuming you can get regulators to accept it:

Map area by area - send out human driven cars if a customer requests a journey you can't cover with driverless cars yet..

Assuming they collect GPS traces, they know exactly what areas will cover the most of their business with the least amount of mapping.

They know the start and end points of the trip and can make a decision whether it can be handled with an autonomous car or a human driver at the outset. They could serve major routes like airports to hotels via autonomous vehicle to begin with and handle everything else with people. That could still represent a massive cost saving.