However given that it is extraordainarily tricky to have succesful long haul with an established competitor next door, I doubt any established carrier could make Liverpool a success.
That was a similar reason that was oft repeated for short haul flights too, but EZY and FR, latterly KLM, have proved otherwise. So it will have to be the right airline(s) in the right place at the right time.
The way its worded points to at least one airline being a Canadian based one.