But, you appear to admit that you passed on the shoulder. THAT is all that is needed for a conviction; one car, or thirty, it doesn't matter.
21755. (a) The driver of a vehicle may overtake and pass another
vehicle upon the right only under conditions permitting that movement
in safety. In no event shall that movement be made by driving off
the paved or main-traveled portion of the roadway.
(b) This section does not prohibit the use of a bicycle in a
bicycle lane or on a shoulder.
As for any dash cam, contrary to popular myth, most law enforcement vehicles in CA - even the CHP - do NOT possess vehicle-mounted cameras. Those that do are not usually set for continuous operation (quite a memory hog) but are activated manually by the officer or when the lights are activated. Some digital systems might also include a few seconds before the lights are activated, but not all. Off hand I do not know what system the CHP uses for those cars they do have.
If you believe there is dash camera footage, you are free to request this in discovery. However, should that footage show you were off the roadway or passing to the right, then you're just hanging yourself ... be careful what you ask for.
About all you can do is seek a trial by written declaration quickly, hope the officer doesn't respond and a court dismisses the case against you, and move on. If found guilty, seek a new trial (aka trial de novo) and then hope the officer doesn't show up (a long shot with the CHP, to be sure). Many courts ill allow you to plead guilty on the day of trial (if you see your officer there) and give you the opportunity for traffic school if you are otherwise eligible. If you go to trial and lose, the court is under no legal obligation to permit you the option of traffic school. So, keep that in mind.
You might also consider a guilty plea with traffic school right off the bat if you want to avoid the prolonged agony of waiting.