I think it's more that BA are reintroducing routes that they used to fly not too long ago, and if not BA, then GB Airways. If LGW (God save us) gets a second runway, then it will stand empty much of the time IMHO.
They cannot command a premium to pay for it so even if charges remain in line with today, I don't see a queue of airlines wanting into LGW. Anyone wanting in is already there. What market dynamic would change with an expanded LGW if LHR continues to bleed new long haul to FRA, CDG and especially AMS? I genuinely and honestly am baffled as to where they think all this traffic will come from as the only growth we see at LGW is in the loco sphere, and yes, that's BA short haul too. (a good thing!)
A few more BA heavies and more Norwegian B787s do not need a new runway and EZY don't want to pay for one.