it won't show it to the cops
This is of course all my ideas, and I don't speak for anyone else interested in non-government driving
Not in their system, but if you had a website or phone database they could access, then they'd be able to see the information they seek. The information could be put behind a password that is only given out to officers at the vehicle owner's discretion so they can look at the information they want. Say somone saw a Shire plate in a hit and run. They would call the police station of course, but when the police learn it's a Shire plate, they would likely have a contact with us in order to call and get access to the database.
The phone number or website address would be on the plate most likely. And like I said, if the government was interested in safety and protection, they would be interested in gaining access to the database in the case of crimes or injustices. They also have less ground to stand on when saying "Well you're not registered, so I have no idea who you are."