Government is involved in regulating Comcast, for sure. But as far as I can tell the issues that make telecommunications hard for new entrants has more to do with the sheer cost of building-out a suitable network than any amount of government regulation.
No, usually the local government actually grants a literal monopoly to a single telecom for a period of time. Their justification is that the telecom is making a big investment in building infrastructure, and there's no way a company would take that risk without some assurances of profit.
Government is involved in regulating Comcast, for sure. But as far as I can tell the issues that make telecommunications hard for new entrants has more to do with the sheer cost of building-out a suitable network than any amount of government regulation.