They'd want to be very careful with the legalities of it.
As a public body, if they were to offer lower fees to Ryanair than to other airlines, they could find themselves in trouble.
Also, no point in pissing off Aer Lingus or Aer Arann. Fair enough if the new routes are genuinely new routes, but if it turns out to be Edinburgh and Paris, they'll be shooting themselves in the foot.