Fight it! Several things to note from a layman's point of view.
Here's a decent website to get you started. Altho this is geared for Canadians, it'll give you a good general idea as to what to do.
Secondly, if you can, revisit the locale where you got caught. Take some pictures with a regular film camera (as digital pix are easier to doctor by and large). Write down everything that happened 10-20 second before, during, and after you've been stopped and ticketed. Do not lie to yourself. If you swore at the cop, write that down. You don't have to use it.... but the more detail you have down, the better you are prepared.
If your state has a law that says if the cop don't show up, charges get drop, then ALWAYS reschedule. Remember that you got burned at a speed trap, and you've got multiple defendants on that day. Chances are it'll be worth the Officer's time to show up and present the case trying to convict you. But changing court dates, you're throwing him off his schedule. Some cops will not show up if they're off duty or whatever. They already got their quota of tickets.
I think you have an extremely strong case in your favor. You weren't physically picked up on radar, which is more than good for you!!
Remember, innocent until proven guilty. The court must PROVE without a shadow of a doubt that you were at fault. If there's an inkling of doubt to the judge that the office MAY have made a mistake, you'll get off. Again, you weren't clocked, you just happen to be presumed guilty by association, and the officer admitted as much.
Good luck, by all account you should win this one.