This is different. It is full surveillance everywhere, for every car and everytime. Not just some roads with cameras. Whose pictures (at least in Germany) are supposed not to be saved except for trucks.
In the US, I'm sure the FBI and DEA have realtime feeds of phone movements for thousands or millions of phones. They had pervasive LPR surveillance a decade ago.
You really believe a phone is truly switched off? Unless the main processor kills the baseband power by GPIO, it is not - and baseband processors are a fairly easy exploit target, much more so for a state-level threat.
I can leave it at home or buy a phone that has hardware validation processes to ascertain its correctness when turned off (or the transmitter system is disabled). I could put the phone in a Farraday cage or selectively raise the noise level of certain broadcast ranges within a limited range. I could kill the radio-IC and use a wifi mesh network. All of these measures are not prevented by federal law.
Federally mandating trackers in a car is a completely different story. It will be illegal to remove these trackers, so a basic liberty will be taken away.
In the US, I'm sure the FBI and DEA have realtime feeds of phone movements for thousands or millions of phones. They had pervasive LPR surveillance a decade ago.