There is near zero chance of AA or anyone else coming in as a spoiler. It was different last time around, Eos and to a lesser extent Maxjet were poaching premium pax where the real money is. There is no need to come to Primera, they can just dump bargain fares on their existing flights at LHR/LGW.
For example I could right now book VS to BOS for £295 including food, drink, bags and entertainment.