They have a 32 bit ID, assigned sequentially during manufacture, with no coordination among manufacturers to avoid overlap. There will certainly be collisions. Those can often be disambiguated though because there is almost no standardization of anything else about the transmission.

The closest thing to a standard is that most either operate in the 315 MHz band (which is mostly older ones in North America and Asia) or the 433 MHz band (there are restriction in Europe with the 315 MHz band). Most worldwide are now in the 433 MHz band. Tesla switched to using BLE, and others are starting to support that.

For the 433 MHz (and I'd guess 315 MHz) there is pretty much no standard beyond that. It is a lot like the situation in wireless weather sensors and other non-WiFi/non-Bluetooth IoT devices.

Different manufacturers use different modulation (AM or FM), different ways to encode bits, and different packet structures.

These can definitely be tracked. I have an RPi with an RTL-SDR dongle that runs rtl_433 and logs the output. I pick up TPMS sensors from cars other than my own that are at least 18 meters away. This was using the small antenna that comes with many RTL-SDRs. I've now got a much better antenna that is picking up many more things on 433 MHz so probably am getting cars farther away now.

There was a study that explored this [1]. They put a network of 433 MHz sensors along roads and in parking lots. They captured 6 million packets from 20k cars. They found groups of IDs that came and went at the same time to fingerprint individual cars and were able to map out driver's daily routines and commute schedules.

Note that unlike cameras and automatic license plate readers this requires no line of sight, so is much less bothered by heavy rain or fog or dirty plates.

Use a good antenna and you should be able to make this work at up to maybe 100 meters or if the cars are in concrete parking structure.

[1] https://networks.imdea.org/your-cars-tire-sensors-could-be-u...

That would be too easy to remove. I'm thinking something like a tiny ribbon with a barcode embedded in the tread. Otherwise it would be trivial to cut the spigot (assuming that's where the sensor is located)

Yep! That's how your car picks it's own four tires out of a parking lot full of tires yelling their pressure.