Cameras, Action: Billings Buses Now Have Cameras

I'm glad to see that Billings school buses now have cameras on board to catch people who disregard red flashing lights at the bus stop signs. I wish the fine was higher, up to $500, but here's my question: why is it legal to use cameras on buses but not intersections for running a red light? They both get a picture of the driver and a plate number. If it works for the buses wouldn't it work at the intersections where it's a problem? Just a thought.