This is one case where it is most certainly not better to ask for forgiveness instead of permission.  It could end up costing you a lot of money in lost production time, footage and fines.

All flight requests and permit applications are submitted to the Irish Aviation Authority by Aerial Filming Ireland.  This process, depending on airspace, can take up to three weeks.

Permit costs can be incurred by governing bodies depending on the end use of the material.  Different bodies have different requirements so it is advisable to check this out beforehand. Ground permits are the responsibility of the production company.

Other useful links are :

Irish Film Board

Dublin City Parks & Rec

Docklands Authority

Filming in Wicklow

Local Authorities