[knorby]

Chicago, as an example, does have cameras on streets in certain areas. Evidence gathered by these is considered admissible without a prior warrant, and no one in the state really debates that, ACLU included (http://www.aclu-il.org/chicago-sun-times-aclu-raises-red-fla...).

There are a lot of stronger counter arguments against this approach that don't have to do with warrants. Cameras don't stop crime, they can only document it and possibly alert to something happening. It is better to just make arguments about the practice of mass surveillance and police priorities than to hope court rulings will knock out cameras placed on public land as unconstitutional.