The government is not a monolith. Being owned by the city doesn't have to mean the cops are in control. The municipality can determin by law exactly who operates the infrastructure, who has access to what, what process they must follow, and how that all will be monitored and enforced. "The government didn't handle this well, therefore they can't be trusted for anything like it again" is a misunderstanding of how governments are constructed and how power can be separated between legislatively mandated structures. Find the source of the abuse, then build a structure to check that abuse.

The structure that prevents abuse is, don't do mass surveillance