The EU does not require us to franchise out our railway system. It simply requires separation of infrastructure from operations for accounting purposes, and open access to the network.
I think, in theory at least, infrastructure & ops could actually be under one roof, as long as the accounting lines were separate, and access to the network was granted on a free and fair basis to all comers. In other words, Railtrack could have existed as a subsidiary of the BRB, with IC, NSE, Scotrail, RR & the freight sector all being separate subsidiaries of the BRB, and access being granted to other outside operators such as GBRf.
All of this is entirely academic really, but it does show that the franchise system we have is only one possible model.