I may be wrong, but I wouldn't be sure that Emirates has had that much of an effect on British Airways at Newcastle, there were actually 4,000 more passengers on the route in 2016 compared to 2007. BA has always had a lot of competition for connecting passengers and I think that BA/EK are after different groups of passengers. BA is strongest on Westbound connecting traffic and likely short haul. Routes like FR to Madrid and EZY to Berlin will probably do more damage!
It would be interesting if anyone had the actual numbers for each destination and how many connected NCL-LHR-XXX