"Provably beneficial surveillance" is the wrong framing.

What you're trying to say is that the harms of surveillance are diminished when the underlying power is distributed enough that cops have to justify themselves in order to access the surveillance powers. That's why we have a 4th Amendment that demands cops get warrants before doing searches and seizures. Think of the difference between a store with a security camera that records to a local network DVR, and the same store but they bought some Ring cameras and send it to Amazon's servers. The former is the necessary amount of surveillance to prove a crime happened, the latter is just enabling abuse.