I just heard this in the case of a no turn on red camera ticket:
Guy took it to the court and explained the judge he remembered the day well; he was sitting at the light, and heard an emergency vehicle coming up behind him. After ensuring the intersection was clear and turning was safe, he made his move; to safely give emergency vehicles a clear way to cross the intersection. That's when the pic was probably taken.
Why was there no ambulance in the pic?
Not sure. May have turned before reaching the intersection?
I can't see that going any way but thrown out.