It was founded on 4 June 1989 with the intention of attempting to preserve at least one example of every type of diesel locomotive to have operated on the Irish Rail system.

When the ITG was first set up, Iarnród Éireann (IÉ) were reluctant to sell any locomotives to the group until they had a location to store them.

[1] The group had also briefly investigated the possibility of sharing a base with the now-defunct Tuam-based preservation society Westrail, but IÉ rejected this.

[2] In 2013, the ITG's siding was disconnected from the Limerick - Waterford line as part of rationalisation work by IÉ, leaving the shed isolated from the mainline network.

G616 is currently stored inside the shed in a partially dismantled state, the results of an overhaul started in 1993 but stopped in 1996 due to a lack of volunteers to continue work on the locomotive.

A museum building at Moyasta is proposed by the West Clare Railway which would accommodate the ITG locomotives stored there.

Restoration work takes place at Carrick-on-Suir and Downpatrick, with Moyasta serving as a storage location for longer-term projects.

In 2010, the ITG sold locomotive 1 to Beaver for eventual overhaul (it had been moved with 2 and 3 in 2005 for use initially as a source of spare parts) and reuse in Sri Lanka.

Today, 2 is operational and carried the name 'Shakthi' at a Holcim cement plant in Puttalam province, Sri Lanka, while 1, stripped for parts during the rebuilding of the other two, remains stored at Merthyr Tydfil.