I think you are missing the most important part here. These cars are always online and share data between them. They have a detailed map of every street and every road bump and every road pole/sign that can be used for navigation. Even if everything is in snow and the camera/lidar is frozen and can't see anything, these cars know exactly where they are and where the road is from predictive navigation based on speed, direction, road shape/bumps from previous data that was collected from 1000s of passes before that on that very same road. At first AI cars will probably avoid certain areas that have not been mapped. Each car will signal any unexpected road blocks, data will be sent realtime to a human operator who will script a walkthrough in seconds. Such as "ok, you are legitimately stuck in traffic right now, just wait" or "ok, there is a crashed car ahead of you so the right-turning lane is closed, move into the left lane and you can turn right from here as an exception". There will be humans like ATC in all cases.

Police and emergency services will just coordinate with the "ATC" to pre-script routes differently depending on the situation.