Where will the growth come from? Will people from Dublin/Limerick/Galway suddenly decide to fly ORK-LON? No, very few will. Will 100,000 extra Londoners suddenly decided to visit Cork? No they won't.
Ryanair will still be alot cheaper, Cityjet realistically will only be Competing with EI, which they will steal passengers from.
I can't see growth coming from anywhere?
I'm sure you are aware what happened with FR to MAN ex SNN, market has grown and fares dropped to 5 euro. FR will be forced to cut fares and attract lots of passengers to STN.
FR will come off worse if WX have the right price structure. An ATR or F50 would be best aircraft in terms of cost.