Apparently the GNR deal with AEC extended to replacement buses for the Hill of Howth tram. They were to get three buses for that. But CIE abandoned the tram system before any replacement buses were ordered. The AAs were in lieu of these, and were delivered in 1961 to replaced the Waterford to Tramore railway.

In relation to Cork, the AU theory sounds more plausible than AR. As AUs were in provincial sercive, it is quite possible that a bus could end up in Cork on service. ARs were in city service (and local rural routes in Drogheda and Dundalk) and would be unlikely to end up in Cork "by accident".