Lets be absolutely serious BA will never operate long haul out of NCL they don't have a history of doing so out of the airport and I am sure there would be other airports in the UK they would look to for long haul way before they even considered NCL.
Even if it's taken a long time for BA to rethink long haul out MAN as yet they are still rumours plus BA have previously operated long haul out of the airport not in the case of NCL.