Chary of admitting or aspiring to ‘greater knowledge’ but Johnson’s book states that shed allocation ended under the UTA. This implies that it existed before. I am not aware of any published lists, of the kind that exist for the GSR in the 30s: IRRS may have GN loco dept records - and the Mallon collection in Louth CC archives may be a mine of information.
I suspect that, otherwise, allocations may simply have to be inferred from the photographic archive - how frequently a particular loco appears at a particular shed. Thus AL class no 59 was, I think, an Enniskillen engine, and has been identified (in Johnson again) as the resident pilot loco. Enniskillen engines could always be identified anyway as the cleanest on the system !