Personally, if the cameras are used only to solve violent crimes and the data isn’t retained for more than 30 days, with no traffic enforcement use at all, then I wouldn’t have much of a problem with this.
That's the catch. They may initially be only to "solve crimes." How long would it be before the local governments realized that they already had information in their possession that could be used to generate revenue? How many would decline going after that "free money?"
And would you trust ANY government agency to delete any data after 30 days?