[adzii_nufc]

Late post but happy to clear some tidbits up from reading through.

CityFibre, Youfibre and other 'altnets' do commonly use existing infrastructure via Openreach and the PIA service offered. Virgin also use this where available. They do also create their own infrastructure, Underground boxes using green or purple ducting marked with their company name on as well as erecting new poles. Openreach on the otherhand wont or very seldomly use third party infrastructure due to costs. The costs Openreach charge to use their infrastructure is significantly lower to the altnets than the charges the altnets would charge Openreach. If I remember correctly Openreach charges are capped on that front due to it being BT and then before that the GPO thus government funded (you can still find a lot of GPO underground boxes and telephone poles marked GPO)

The obvious downside to a lot of this is large areas of the UK were built with cables buried directly in ground, an altnet comes and lays trenches all over the place and installs ducting, 5 months later you get Openreach digging up the same footpath to do the same.

Everyone builds the network quite differently too. Virgin use sub ducting and tubing to blow fibre bundles through. CityFibre often do this but also mix with physical sheathed cables. Netomnia on the otherhand build some areas almost identically to Openreach, using the same CBT's and fibre nodes in areas Openreach havent yet reached, but have been seen to be using blown tubing in areas that Openreach have FTTP. Almost like they're wanting to be bought out at some point.

There were also once areas with no BT/Openreach provider for periods of time. I cant imagine they were that common but a few north east towns built from scratch in the 50's up over were essentially forced into these alternative cable providers that would provide a service back to the BT exchange whilst selling their own television products or television reception. BT/GPO eventually did provide services at later dates but Telewest/NTL/Virgin got a strong foothold in these areas with broadband later down the line.

The last one incredibly is new housing companies creating their own altnet and bundling that in with a home purchase, forcing you to take their product or nothing when purchasing the property, the most notorious for this is Persimmon homes which have next to no Openreach/Virgin or other altnet FTTP due to having an exclusive deal with their own provider as well as not having the council adopt the estate roads for a fair while which won't allow any other provider to build for a set amount of years.