No, you don't generally don't need to invest a lot of resources to lobby yourself. (There are other politicians with power to do things than "congresscritters". In this case the relevant body would be ... the municipal owners.)
When state legislatures are passing (bought) laws barring municipalities from doing exactly this sort of thing, then no, the relevant body is not, in fact, the owners.
Actually, TN is one of the states that has passed laws against municipal broadband. From that article:
It’s illegal because Tennessee prohibits municipals from delivering both electric and internet service in any “area where a privately-held cable television operator is providing cable service.”
