As far as I can see "the powers that be" already have 90% of the information that they are telling the transfer companies to collect on their behalf but the vital bit they don't know is the address where an independant (non package/hotel) traveller will be staying. They then simply fliter out all the registered addresses and go and pay a visit to the unregistered ones to check if the owner is there. If they are, apologise for disturbing everyone but if not, chuck out the visitors and fine the owner.
At a stroke they have changed a "hit and miss" investigation into a targetted one. Very clever.