Indeed OCH, if a pilot job is worth having they will stay but the fact is that Ireland is too small to provide sufficent Irish pilots who can satisfy EI's particular requirements. Certainly in terms of self sponsored pilots. Irish recruits though are far more likely to stay and make a career of it even if the job isn't the best around.
Aer Lingus has a well known preference for integrated course graduates which also restricts them. On top of which their selection process with it's reliance on psychometric test even for DEs, narrows it again. That means they have to cast their net even wider. So they must hire non Irish quite simply because they exclude the majority of Irish candidates before they even get to the starting gate.
Non Irish pilots are more likely to move on to pastures new particularly for better pay, prospects and possibilities of earlier command.
So logically the most likely candidate to stay on and make a career of Aer Lingus is probably Irish. But of course by the very nature of their recruitment process they exclude much of the Irish self improvers. The very people who would want to stay and see out their career in Aer Lingus.
This recruitment drive seems to be a way solving this problem of their own making. Tie them down with bonds and maybe they'll stay a bit longer whether they be Irish or British or Polish.
It's rather ironic that there's a high failure rate on their courses given their recruitment process. So much for integrated graduates being better!