Much of the GNR network was closed in 1957 and the remaining system was split between Córas Iompair Éireann (CIÉ) and the Ulster Transport Authority (UTA) in 1958, with the fleet divided as equally as possible between the two parties.
The UTA based some of its S class locomotives in Belfast and used it to haul trains on the Belfast - Portadown main line and Portadown - Derry "Derry Road".