I think I just saw one of these, a black Model 3, driving at night on surface roads near Palo Alto in SF Bay area. Had a similar roof rack with a single sensor mast sticking straight up. License plates looked like regular recent California plates (9XXXYYY). But on the drivers side door were lettering "Fleet Validation" something something....
Which leads me to think it's a Tesla-owned fleet validation vehicle, as when I google, I found
Additional Resources | Tesla Other Europe
and if you read the privacy notice, it says
"These cars are owned and operated by Tesla, clearly marked, and are equipped with sensors and cameras to conduct fleet testing in real life environments. Their purpose is to gather road data for research, testing, and development in pursuit of advancements in vehicle safety and technology"
So I think
@Supcom had it right on, and the privacy notice actually says a lot about what it's doing, in order to explain what it is NOT doing - i.e. NOT collecting personally identifiable facial or other information on YOU.