This is a non trivial issue and I am awaiting a CSO release Before I tackle it. The County is also equally wrong on its inner boundary.
For data consistency I need the new LAU2 codes first. An example.
The Electoral Division of Ovens is now split into 2 parts…but not on OSM where a city boundary technically floats inside the county. Unconnected
Before I tackle it I need canonical data on ED names and LAU2 codes. The old electoral division splits in 2 so there will now be a City Ovens and a County Ovens with different LAU2 codes in the Ref Field.
Each townland will have to be split city and county parts to maintain data consistency.
Every old townland and ED will remain on the map as a boundary=historic entity. I should flag this up to Rory before I do it. I might have to add a freeform tag field like a logainm:2014=split so he can spot them clearly.
For a rough idea of what I propose please examine the Galway City boundary on the West side where the then Barna ED was split in the 1980’s and note historic boundaries there albeit pre the advent of LAU2 codes.
I am still in research mode on this Cork City/ /County but don’t worry as I will delete nothing…merely retag. Every political boundary LEA/MD for sure and Constituencies will have to be rechecked too.
Official Ireland has had 10 years to sort all this out…and still haven’t. But a resolution is near. 
If anyone is interested in the big final schplit please feel free to comment and I hope a final tagging scheme presents itself from this discussion.
Regards from the Fog in the Bog. 
