40-6-20(a) appears to the appropriate section for obeying a traffic-control device. 40-6-20(f) covers the camera monitored intersection and is specified as a civil violation only (as is the practice nationwide with camera monitored intersections). 40-6-21(a)(3)(B) states that you must come to a complete stop before "cautiously entering the intersection" to complete a right hand turn. It sounds as if the ticket would be valid.
While I see this as extremely strict in your situation, it appears the officer was technically within his rights to cite you. Further, an officer may pursue a violator (with or without blue lights) outside of his jurisdiction and cite an individual for a violation within his jurisdiction. What matters is where the violation occurred.
The license plate issue appears to be covered by 40-2-41. Obviously I have not seen your bracket, but unless it obstructed the information displayed on the plate or covered it with something other than a "colorless and transparent" material then I presume the officer's warning was misplaced. You may want to get a second opinion from another officer on your plate bracket before taking steps to remove or replace it.
Basically it sounds like this officer was being a jerk. The best approach would probably be going to court, admitting to everything you've stated and simply ask that the ticket not go on your record. I cannot imagine the traffic judge will not let you pay a small fine and dismiss the ticket.
Please reply if I can help further.
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Edited by JD on 3/18/2010 at 1:43 AM EST