They were dated around the time of Charlie Haughey, which led one to suppose that the art-mad Taoiseach was not only interested in Gandon’s mansions but also in cutting-edge architects. Having a significant public building in Ireland built at that time by the then-unknown Hadid would have left an interesting architectural landmark in the capital, but it never happened.
Now, with the publication of the government papers from 1979, it appears that it was Haughey who scrapped the plan and it must have been either Jack Lynch or Liam Cosgrave who commissioned the competition.
[Haughey] summarily dismissed a £4 million plan to build a Taoiseach’s official residence and State guest house on the site of the former Apostolic nunciature in Phoenix Park. This had been the subject of an architectural design competition and a winning English design had been selected.
I am assuming that the winning design was Hadid’s, though no mention is made of her in the Times piece and this discussion at Archiseek suggests that the competition was won by Evans & Shalev Architects, with a Rem Koolhaas entry also commended [Update: OWA's website has extracts from his entry].
It seems quite the missed opportunity that the residence was not built at the time. Instead, around 27 years later, the Taoiseach gets the dull, if dependable, Steward’s Lodge on the Farmleigh estate.