Bear in mind that EK have increased capacity by between 30% and 60% depending on the 777 layouts that they use- that increase in loads could have been comfortably been carried in the A330s that previously operated (I reckon it equates 75%/76% seat load factor based on the 278 seat version of the A330).
Has there been any general discounting of EK fares from Newcastle since the arrival of the 777s? This route was hardly in need of increase in capacity unlike a lot of the other regional UK routes, so I imagine the greatest driver would be cargo carrying capability.