All they can do with their power is what the government allows them to do through manipulation of federal, state, and local laws, as well as zoning, ordinances, codes, etc.
Unless they own the land itself, they can't prevent others without the use of government as their tool.
"The government" in this case is responsive to the 99% of people that do not care one bit about ISP monopolies, but do care greatly about road construction in their neighborhoods. This regulation exists for a reason that isn't just pure mustache twirling corruption.
Unless they own the land itself, they can't prevent others without the use of government as their tool.