The coverage by bus is expanding fast. The thing is that much of the coverage is not by Bus Eireann, as in the past, but by smaller operators.
But there is a National co-ordinating body called Transport for Ireland who have all the timetables and a route planner on their web site.
Killarney, Tralee and Ennis are also cases in point- you don't have to go by train or wait for the twice daily flight to Kerry. All three now have regular bus services to Dublin Airport, as fast if not faster than the train, and more frequent.
And there is a National stored value card to pay fares on just about all services, called the Leap Card- which also gives a 30% discount on cash fares on TfI services (not commercial services like Dublin Airport to Galway). That card is available to anyone.
Many people will be aware of the Leap Visitor Card in Dublin- well this is the national equivalent scheme.
The divide between citybus and coach services in Ireland is also very muddy with many even local services now being operated with coaches.