If you really are concerned about this then you should be advocating for open access networks, i.e. separation of physical assets and service provisioning.

The municipality owns all the hard assets, such as ducts, pits, poles and fiber optic cables. Private service providers then sell Internet access and other services that on top of that.

The municipality cannot leak or hand over information it does not have.

Open access is a tried and true concept, easy to implement. However, you should also be working on better local governance, since that is the root cause.