I think the long term solution to the privacy problem is going to be to switch to a vehicle marking system which can only be usefully used by law enforcement. Example, if instead of license plates you had a transponder that sends out encrypted metadata about the vehicle in a way that only law enforcement could decrypt it. Obviously there are still problems of abuse of law enforcement keys but it raises the bar significantly and it prevents private companies from building a business out of collecting the data.
You introduce a new problem, which is that eyewitness reports of crimes etc can’t identify the vehicles as easily, but that could be viewed as an acceptable loss. Or the problem could conceivably be solved with more technology if we can have dynamically changing license plates (which, again, require law enforcement keys to map back to a real identity for the vehicle).
The only other way I see is that we change laws so that a company like flock collecting this data and then offering it to the government is treated the same as if the government collected it itself. But now that the cat is out of that bag and there is big money behind it, I don’t really see it going back.