Transit directions are available in a few cities like Dublin and Cork, including transportation provided by Bus Éirann, Aircoach, and more. There's also support for city-specific transit options like Dublin's electric rail system the DART (Dublin Area Rapid Transit) and Dublin Bus.
Unfortunately, most of the transit options in Ireland are facing service cancellations in the face of Hurricane Ophelia, which made landfall around 1 p.m. local time. Many transit advisories listed in Apple Maps mention cancellations lasting from 10 a.m. to at least 7 p.m. local time in Ireland.
Apple has been adding public transit directions to new cities around the world since the feature first debuted in iOS 9 in 2015. Some of the latest areas to get the feature include Taiwan, Ottawa, Edmonton, Québec City, and Hungary.