Note that breaking even over 20 years in this town requires 72% of households to sign up, according to the article. Even if someone managed to cut costs by half, that's a town that can only ever handle two ISPs - maximum - with their own infrastructure at once with everybody signed up.

You could think of a system by which multiple ISPs could sell service over the same city-owned infrastructure, but there's no real benefit to that. (And I say this as someone living in a country where that essentially happens.)