From what I've read in Car and Driver, many of the red-light camera schemes are done at NO cost to the municipality. The system vendors install and maintain them for no charge other than a percentage of the revenue they generate.
Yes, they get a private collection for public fines.
And this is no cost because???????? Okay, no up front cost.
Seems to me that it makes the whole system suspect that the camera providers, the ones doing the maintenance and installation have a financial interest in fining people for traffic code enforcement. As a prosecutor, I'd have a hard time selling the "independence" and "lack of bias" of that witness.