Hi Cyrano
I've no idea how helpful they are in response to any particular query, but for what it's worth the statement I had in mind was this one:
Market Research | Fly to Dublin
Our market research allows us to monitor the trends of our passengers. The graphs below give an overall view of passengers travelling through Dublin Airport, however if you would like more detailed information on any one of our number of markets please let us know and we will provide you with further information.
I also notice that the IAA (which I'd take it is broadly similar to the CAA) states that it doesn't supply passenger data. Their site actually still tells people that the daa would supply data on Shannon! And, indeed, CSO data on air traffic doesn't seem to include related county.