[gordner]

Here in Canada, they enforce them by not allowing plate or license renewal with an outstanding balance. Total revenue generating scheme, as stated above has proven to increase rear end collisions at lights. No safety improvement has been shown from installing them at all. No front plates here in AB, they only ever photograph the rear. You can contest in court here, but to do so you either have to admit you were driving, then the ticket that was simply a fee is now a points offense automatically, or you can out who was driving and the ticket will be issued as a traffic infraction to that person with points attached.
And here I believe it is the same, the lion's share of the revenue landing in the pockets of the camera manufacturer not the city.