The BIR is different to the IMC rating that has been available in the UK for a while but it's great news that there's finally a European equivalent. I don't think any of the Irish ATOs are teaching the BIR yet but it's certainly valid for use in Ireland.
To answer your question about the weather types you are permitted to fly in:
(5) The exercise of BIR privileges shall be subject to all of the following conditions:
(i) the decision height (DH) or minimum descent height (MDH) used in aerodrome operating minima shall be at least 200 ft greater than what would otherwise be calculated according to point ‘NCO.OP.110 Aerodrome operating minima – aeroplanes and helicopters’ and point ‘NCO.OP.111 Aerodrome operating minima – NPA, APV, CAT I operations’ to Annex VII of Regulation (EU) No 965/2012; and
(ii) the visibility used in aerodrome operating minima shall not be less than 1 500 m;
(iii) the pilot-in-command shall not commence a flight under IFR or undertake a VFR-to-IFR transition, unless:
(A) at the aerodrome of departure, the visibility is at least 1 500 m and the cloud ceiling is at least 600 ft, or the published circling minimum applicable to the aeroplane category, whichever is the greater; and
(B) at the destination aerodrome and at any required alternate aerodrome the available current meteorological information indicates, for the period from 1 hour before until 1 hour after the estimated time of arrival, or from the actual time of departure to 1 hour after the estimated time of arrival, whichever period is shorter, a visibility of at least 1 500 m and a cloud ceiling of at least 600 ft, or the published circling minimum applicable to the aeroplane category, or the DH/MDH incremented by 200 ft in accordance with (i), whichever is the greater.
I've heard on the grapevine that the IAA require that all seven IR theoretical knowledge exams are taken. Although FCL.835 states that while the relevant knowledge of the seven IR subjects is required, only three exams need to be taken based on the three flying modules.
Hope this answers your question.