Well, they don't need to build out conduits + fiber, only fiber since the idea is encourage their monopoly over the last mile. They just need to do what is happening today on the private side and run a fiber (which is cheaper for each individual player). Then encouraging everything other than the last mile to be private sets up all the right incentive structures as far as I can see to solve a lot of problems of broadband internet access.

You can see this model in very similar markets, where some countries run the cell network as a national utility. But your actual carriers are a large choice of companies connected to that network that differentiate on service, price, and added on features, rather than the amount of capital available for infrastructure investment.