I think what the author points out is that there’s a problem with leadership and accountability here. Subways are an essential city utility, and citizens expect

I think what the author points out is that there’s a problem with leadership and accountability here. Subways are an essential city utility, and citizens expect them to meet certain standards (capacity, pricing, etc.) and then will elect political leaders who are accountable to those standards. If subways are publicly run those leaders have some authority to make changes, as well as to be held fully responsible by voters if things don’t work. (Not saying this system is perfect either.) In this particular flavor of privatized system, citizens still have the same expectations of functional infrastructure. (A subway line is, after all, a city project even if the city chose to outsource it to private interests.) So they will elect leaders to address perceived problems, except that the leaders won’t have full authority to change things. At the same time the private firm won’t have full control over pricing and won’t be incentivized to improve service. Hence the example of a private line wanting to raise prices and being blocked by the city, but the city leaders being unable to take direct action to improve the service itself. Presumably there are ways to implement private provision of public services that don’t end up like this. I would imagine the key is not handing control to private interests who can’t ultimately be held accountable. This article illustrates one of the bad outcomes.