No, it’s way more complex than that. In the UK, the public phone network was privatised in the 80s and 90s; the assets are owned by the private company Openreac

No, it’s way more complex than that. In the UK, the public phone network was privatised in the 80s and 90s; the assets are owned by the private company Openreach, with various regulatory requirements to provide access to the network to third-party operators. Providing access to that network is a chargeable service. So yes, third-party operators contribute to installation and maintenance cost.