There's no such plan. Even some of the reopenings that were listed under the Transport21 plan may not take place. (Phases 2 and 3 of the Western Rail Corridor, Athenry-Tuam and Tuam-Claremorris, are unlikely to happen, though I would question whether or not the latter section was ever a viable proposition). Likewise M3 Parkway-Navan is indefinitely delayed, while the DART Underground and various Dublin Metro schemes seem doubtful (Metro West is officially cancelled). So with these schemes hanging in the balance, I can't see anything happening for West Cork for the forseable future. The rail enthusiast in me would love to see it, but the taxpayer thinks otherwise, indeed questions are being raised as to whether or not Athenry-Ennis was worth the money spent on it, given the numbers using it.
Incidentally, there are other areas of Ireland without rail links, in fact you can travel north from Mullingar to Derry without crossing an open railway line.