As far as I know (and it's a technicality) CIÉ never had any Mark 2A's - only Iarnród Éireann did. Prehaps that might help your search. Mark 2 details that were bought from BR:
Open Second Mark 2/2A (64S, 2 Lav, 31 ton 17 cwt)
4101 (5428) - AD2A
4102 (5411) - AD2A
4108 (5252) - AD2Z (48-seater originally)
4110 (5306) - AD2A
Open Second Mark 2C (54S, 2 Lav, 32 ton 16 cwt). All AD2C
4103 (6406)
4104 (6405)
4105 (6401)
4106 (6413)
4107 (6403)
Open Second Mark 2A (54S, 2 Lav, 32 ton 16 cwt)
4113 (19469) - AA2A (Built as Corridor First, then Corridor Second)
4114 (13471) - AA1A (Built as Corridor First)
Open Second Mark 2B (42S, 2 Lav, 33 ton)
4109 (19512) - AA2B (Built as Corridor Second)
Open Second Mark 2C (52S, 2 Lav, 33 ton 9 cwt). Built as Corridor Seconds (AA2C)
4111 (19521)
4112 (19553)
Buffet Open Second Mark 2B (36S, 1 Lav, 35 ton 10 cwt). Built as Corridor Seconds (AA2B)
4401 (19489)
4402 (19497).
All purchased in 1990 from Vic Berry Scrapyard, Leicestershire. As far as I know, they were on 'secondary' services to places like Galway, Westport and Waterford. Believe they were withdrawn between 2003-2005. 4111 damaged by fire and scrapped 1992
Regards,
Kieran