In the crew room, we have a copy of a document called the
Irish Aviation Authority (Personnel Licensing) Order 2000.
The following is taken directly from it:
Flight under Instrument Flight Rules
19. (1) A person shall not act as pilot-in-command of an aircraft or as co-pilot of a multi-pilot aeroplane or helicopter registered in the State under instrument flight rules unless such person holds a valid instrument rating -
(a) issued or validated by the Authority and endorsed in or deemed by the Authority to be included in the licence held by such person or in the validation of such licence, as the case may be, and
(b) appropriate to the category, class or type of aircraft flown.
(2) A person shall not, within the State, act as pilot-in-command of an aircraft or as co-pilot in a multi-pilot aeroplane or helicopter registered in any other state under instrument flight rules unless that person holds a valid licence, with a current instrument rating endorsed thereon or included therein, issued or validated by the competent licensing authority of the state in which the aircraft is registered and appropriate to the category, class or type of aircraft flown.
So, I would say that it looks pretty definitive. The IAA have standardised on the JAR model as Scopeland says. It is the UK who are at odds with it.
You need an IR to fly under IFR in Ireland, regardless of the weather conditions.
Love
Charlie