If it becomes clear that it's impossible to get the aircraft they want - the 330/340 (and this looks to be likely), then why not go to the other extreme and get a larger aircraft. There are about 20 747-400s in storage; okay, not the most likely option, but if it's a choice between ceding new markets to possible entrants, what do you do? Cede, or get an aircraft bigger than you might otherwise need.
Another possibility might be to wet lease them from Air Atlanta, on the understanding that it would be a short term fix, pending the addition of new aircraft.
Surely, EI would be able to fill these aircraft to JFK, ORD, MCO or BOS. The runway at DUB is obviously a concern, but using a -400 might give EI an opportunity to experiment with long haul low cost services.