Either Dublin to Rosslare, Mallow to Tralee or part of Rosslare to Limerick Junction would get my £££ out. However to give a decent traffic density it’s probably going to have to be something around Dublin. And yes definitely classic loco hauled, those lovely little 121, 141 and 181s thrashing away on 3 or 4 coach rakes of Park Royal and Cravens stock.
The Enterprise Line since it's the only Trans Border route here. Belfast Newry Drogheda-Dublin. Train Safety Systems involved are Northern Ireland UK AWS DSD to Republic of Ireland CAWS