[WillPS]

That’s a different part of the network though. LLU as a concept effectively died when FTTC/FTTP came along, but it appears the core networks are still separate from each other. Without inside knowledge of how it actually is set up, the fact that IPv6 is not available on EE and Plusnet (while BT itself has had it enabled for years) would suggest it to be the case, as IPv6 enablement is a big task and it’s not worth doing if the medium/long term plan is to shut it down anyway.

I don't think that's true. LLU (local loop unbundling) means sending the user's line to a backhaul other than BT's at the exchange level. FTTC and FTTP lines still terminate at the exchange. I have FTTP with a Vodafone reseller, and my Openreach line connects to Vodafone's infrastructure at the exchange down the way. (wrong, corrected in the thread)

EE, Plusnet and other BT Wholesale customers connect to the same infrastructure as BT (retail) customers.