> privately-owned surveillance cameras that are "voluntarily" offered to law enforcement

You may find interesting to know that in the case of crimes being committed near or next to a business, especially independent businesses, their priority is often to minimalize risk to them and their business, and so they do not provide any recording, or use rolling footage which wipes every x days (often just one day). That way the footage is useful to them, but they do not have any additional obligations.