While you do own the hardware, you probably don’t own the data, licenses, and software in the SIM so you might not be entitled to the data it transmits once it hits the carriers network.
Well,[the data it transmits] it's personal information, so the owner of the car has a very explicit right to it. (Car plates are from an EU country.)
Or maybe just ownership of the car is enough? I kind of suspect it might not be though.