Yes, while I'm not a fan of fully networked, recorded, ubiquitous license plate tracking, it is quite different than the cell phone.

License plate number is a registered identifier mandated to be fully plainly visible, with that identifier tied to a registered individual; compared to cell phone which has identifiers, sure, but they're not registered to an individual necessarily, and not mandated to be plainly visible, rather only "visible" as a means of service provision.