So in the UK it's a bit weird: all the lines from the cab or exchange are owned by OpenReach, but carriers can set up their own backhaul from the exchange. Thus

So in the UK it's a bit weird: all the lines from the cab or exchange are owned by OpenReach, but carriers can set up their own backhaul from the exchange. Thus, if you have an upstream issue with one provider, your other provider may be still unaffected. I would have drawn the diagram like this: Network // Carrier // OpenReach // Network Provider1 Internet <--> <--| Exchange <--> Cab |-> CPE Provider2 Internet <--> <--| BT and TalkTalk operate their own carrier networks for back haul, and networks like AAISP can let you choose which carrier to use for a line, hence why they offer the dual WAN CPE.