Although the South Waterford Line is fictional, it is very much a could have been. The first proposals for a railway between Cork and Waterford envisaged a line through Youghal, Dungarvan and Tramore. Only the lines from Cork to Youghal and Waterford to Tramore were actually built, the through line being further north from Mallow to Fermoy, Lismore, Dungarvan and Waterford. The Act of Parliament to build the line from Waterford to Rosslare allowed for a short cut from Fermoy to Cork. If that had, instead, been from Dungarvan to Youghal, then you have the South Waterford Line.
Stephen