Couldn't they do like they did with drinking age laws and restrict federal road/other funding to jurisdictions that don't implement police camera programs?
Also, the police are going to fight cameras tooth and nail. Major demographics from both parties are going to be mobilized (unions & crime hawks).
The liquor laws were much more sympathetic and even they took a long time for full federal compliance.
The petitions are not bills that people are submitting to the floor of Congress. To say, "well the petition didn't ask for this specific implementation," seems a bit disingenuous. Federal legislation requiring it to receive specific funding would effectively be "federal legislation requiring it" so I'm unsure why you're splitting hairs.
True. They're not much of anything else, either.