You asked how profits are extracted, and I answered your question. Now you're bringing up monopoly vs free market, which has nothing to do with the question.
The award of the contract to run that particular collection of routes is ostensibly free-market. Once it's awarded, they hold a monopoly for the duration of the contract though.
Actually, the very widely replicated experience of most challenger utilities is that the entrenched utility will stop you, sometimes in collusion with the government or municipalities. Try getting permits to dig up the road to put your competing pipes alongside the current monopolists.
In Britain, British Telecom spent around 20 years making it impossible for other players to supply an internet service to consumers. They used various anti-competitive practices and had very good capture of the largely toothless regulator OfCom. This is all documented.