All office and other accommodation occupied by the Department of Transport is owned or leased by the Office of Public Works (OPW). The Department itself is primarily based across our three offices in Dublin, Shannon and Loughrea.
It is also important to note that some of the bodies under the aegis of the Department may hold a large number of buildings spread out regionally such as offices, depots and workshops, while some others may operate and manage a single site with multiple distinct buildings upon it, such as the ports and airports, which also includes the possibility of co-location with non-state bodies such as service operators.
In order to most accurately provide the information requested, I have referred this question to those organisations for direct reply.