The company pays but then it can also use other companies' fiber, so sometimes it's worth it to do so in order to show that they have coverage in a certain area where there might not be fiber (that they then lay down), and also that they cover everywhere else.

It's quite a clever system that uses market greed to incentivize building. It's the same system as railroads, imagine if railroads could not share tracks with each other.

https://en.wikipedia.org/wiki/Arrangements_between_railroads...

Grants from the government.

Some places also vote to have the city or town connect with Fiber which then puts tax money aside for it.

In many places it is the power companies that run fiber and they are mostly partially or fully state owned. The lagest ISP also has the state as the majority share holder.

Usually there's a separation between transport (physical) and the service (billing and so on). Not the same companies. At least, in Italy there is.

It's the same for power, one or two companies lay the cable, myriad others sell the service.

Here in New Zealand the tax payer contracted a lines company to do it. ISPs compete on service but we don’t get 25 - maybe 4 or 8Gbps.

In my case it was the city. I'm not sure if the providers pay for access or is it free (paid for by taxes).