The thing is, if (for whatever reason) Ireland were to find itself reverting to the Punt Nua, as far as I am aware, an acccount with RD or NR would be regarded as an Irish account and would be converted out of Euro - like it or not. This is because although the mother bank is Dutch and British (respectively), it is still and Irish branch. Danske Bank is the mother of NIB - but in the event of a reintroduction of the Punt Nua, any accounts in NIB would be sucked in also. Guarantee to refund in the event of insolvency does not mean guarantee in the event of the host country changing it's currency.
The real question is, if you were to open and account with a foreign bank which did not have a limb in this country, would you be protected against having your deposit repatriated and converted to Punt Nua?