It's all froth. "Look at the shiny dream voters, here's what you could have one day" (I'll Be long gone by then but vote for me in the meantime)
London needs Runway 3 at LHR ASAP. The CBI is putting the thumbscrews on the Tory party, many of whom are not as "eco mental" as "call me dave". Anyhoo we'll have T2 in two years, T5 is working well now T5C is up and running and connectivity is being improved if BD folds into BA.
No airlines believe this Fantasy Island will realistically happen. BAA doesn't even believe it, if they did, they'd be trying to run it. Now Boris famously does NOT do detail, he's broad brush and lazy. (I do love him though!)
Incidentally, there is no actual policy as yet, that's why we don't know whether this proposal depends on a closed LHR.
Incidentally I know CDG has all that space, but it's not really that much better as an airport experience, it's just spread out more. I think Silverstrata's view of LHR is about five years out of date. The complaint about T2 being a poor experience, present tense shows that much.