This is the reply I received from a licensing officer at the IAA:
Dear XXX,
Thank you for your e-mail.
Under the Bi-lateral agreement set up between the UK CAA and the IAA in October 2005, should you sit and pass all 14 of the JAR ATPL examinations under the auspices of the UK CAA and intend to complete your practical flight training in Ireland, then the IAA will accept your examination results as part of your CPL IR training. Ireland will be the country of licence issue.
Regards
XXX
Aviation Executive
Examination Unit
Tel: 00353 1 6031169
Fax: 00353 1 6777484