The data is currently readily available.

In the case of municipal broadband, you could vote for local politicians that are against dragnet surveillance.

Also, paradoxically, the 4th prevents the government from gathering data, but not purchasing it. In the case of municipal broadband, there is a strong argument to be made that you are constitutionally protected against invasive privacy policies, such as logging or selling personal information.

In fact, yes. C.f. there many laws about mail tampering for the post office. When the government has to deal with the data in "normal, non-criminal" situations, and not just "special investigative" ones, there tends to be better safe-guards in place.