Could this be a play for some of NAL's aircraft orders. According to SAS latest 50ac purchasing announcement they struggled to get early deliveries since both Boeing and Airbus order books are pretty full. BA could need some quick respecced deliveries of 787's to compete with Qantas UK-Australia direct = before 2020. Plus some 737 long range orders woudn't go amiss for additional trans-atlantic point to point routes.
And with the high % short selling of Norwegian stock, BA where hardly going to loose on their investment combined with a takeover threat.