The cars themselves phone home all the time. You have to physically remove the transceiver to prevent it or run a jammer nonstop at the risk of a felony.
The APL readers still get you without the cars transceiver. Plus if you have automatic tire pressure sensors, those are mandated to communicate in plaintext over rf when sending the data to the car, from my understanding, and you can farm those to track location by setting up radios next to roadways.