What about them? Once they're sited and hooked into the lines, replacing the gear inside is not difficult.
The question is whether a regulated monopoly could provide good broadband connectivity at a good price. Equipment upgrade scheduling is an implementation detail.
And it's a detail that is already priced into the service. It should be possible for such a monopoly to provide the same level of connectivity as Verizon or Comcast at lower prices, because for their current prices Verizon and Comcast already provide that level of connectivity plus content and software and marketing.
Big ISPs do everything necessary for connectivity, but they also develop and sell products that run on that connectivity. For example Comcast's on-demand and DVR everywhere solutions compete directly with services like Netflix, HBO Go, NBC.com, ESPN 3, etc. Developing, maintaining, and marketing that costs Comcast a lot of money--money that a connectivity-only monopoly would not need to spend.
It would be like if your electric company owned the lines, owned the power station, and sold you appliances like TVs and washing machines. Instead, electric companies just sell electricity, and everyone else sells you things that use electricity. I can't think of a reason that a similar architecture would not work for the Internet.