Ok. How's this for a very "possible" scenario.
You're driving a different route (due to road construction/etc.) And your car goes past a house that is under surveillance for some crime (Say prostitution or drugs).
Your car's plate gets "snapped" in front of the house. They don't CARE that you're just driving by, You're driving past a crime scene. They get your data, and then they check your plate and find you had unpaid parking tickets. Then they visit you at your place of employment or better yet your home. They ask for you in regards to a crime at house where Prostitution/Drugs are used.
Does it MATTER to the police that you were just driving by the hose ? Nope. They can use it as an excuse for harassing you.
Does it matter they already knew your plate # ? Nope. They can use the cameras to determine ANYTHING they want:
"Gee. You drive from Camera A to Camera B, a distance of 1 mile. You drove it in 45 seconds, It should have taken you a full minute @ 30MPH. So you're speeding - DING ! Ticket issued. Camera B to Camera C, another Mile. Another 45 seconds, DING Another ticket.
Is that OK with you now ?