So- I if I understand correctly, in fact there are no limitations on routing for a trijet across the Atlantic in the form of ETOPs-type route limitations? Therefore this aeroplane turned effectively into a trijet flying the route from LAX-LHR. as thousands have happily done so over the years.
So where is the problem?
People are coming up with suggestions of routing 'standby' aeroplanes- quite some suggestion at $200 million a throw. And of course whole crews are just lying around waiting for a call!