Before that even. CIE ordered 60 diesel railcars in 1950 from AEC-Park Royal (same company) which came in 1952 and ran as 30 4-car sets with existing coaches in between. These took over a surprisingly significant proportion of the sparse long distance services, including the Dublin to Cork expresses, even there only a few per day. I believe the railcars had small steam boilers to heat an adjacent carriage, which had through mu wires simplistically tacked underneath but were otherwise unadapted. When the diesel locomotives came a few years later things cascaded downwards. The railcars were an intermediate stage of development by AEC between the GWR cars and the later mass build of BR multiple units. They only had the 125hp engines of AEC buses of the era, and must have seemed significantly underpowered with carriages marshalled in.The A Class introduction in 1955 made them practically redundant, Tailté being withdrawn in 1955.
The railcars had various different configurations, and in typical CIE style as described above they then got all sorts of individual rearrangements and rebuilds such that, again, hardly any two were alike.
The three 800 4-6-0s were seemingly hand-built, about one per year, and it's surprising Inchicore had the tooling and dies to build boilers etc of this scale. Significant parts for a fourth were built which went into the spares pool for them. In the 1960s Ian Allan book on loco names it listed the 10 loco names proposed for the class, which would actually have been an overkill for Dublin-Cork expresses of the era, and they were too heavy to run elsewhere. There were newer Irish locos, as the Great Northern continued to build steam postwar at Dundalk, which ran north from Dublin, and Harland & Wolff at Belfast helped out with some heavy mechanical and boiler work. The figures given for locos out of service are not meaningfully compared to the UK as procedures differed, locos were generally just used less and laid aside as they became obsolete, but not formally withdrawn from stock, they were fully depreciated in the accounts and might be capable of steaming once in a while, or just sat in a shed for years.