When the Troubles flared back to life in the late sixties and early seventies, did the Irish government have any plans to deal with either a sudden British withdrawal from Northern Ireland or a dissolution of civic authority there?
When the crisis in Northern Ireland escalated in the late '60s/early '70s, the dáil actually put in plans for an invasion of Northern Ireland to protect Catholic communities. I'm not very familiar with the issue, but here's the Wikipedia article on it if you're interested.