To get better compliance, you have lots of queues that use scanners and nearly none (working) for those that want to opt-out.
Anyplace there is a choke point will be fitted with cameras and scanners.
The data formats will be antiquated and well documented (there will be documents for the companies bidding that specify all aspects of how the data will be managed). Some gov worker will one day be taking home a laptop/tablet with millions of people's information and it will be stolen from that worker's car as they stop to ___________________. Usually, they are stopping at a church and they will have left the device in plain view on a seat. The info will get sold to commercial entities which have their own scanning network in shops, car parks, etc and can combine the government data for a more accurate fix on who they are scanning. In return, the government can subpoena that information and get a wider picture of anybody they like whether they are on public or private property. Add to that the spy devices that people have paid for and fitted themselves and it's "A Brave New World".