I have no real data, but I'm confident that most of them are going to Dublin. The number of cars there seems fairly consistent from day to day. People from nearer to Port Laoise and Templemore would, presumably, use those stations. Southwards there's only really Rathdowney - northwards, there could be a few from Roscrea, perhaps. There are a lot of people that live "in the wilds", as well, of course. I don't actually know anybody who commutes through there - there is a bit of hospital traffic, which is probably fairly steady, though it will vary from day to day.
My drop-off and pick-up was for a hospital trip and, as they had to be in Dublin before 9am, we arrived for the 06:40, most of the cars were already there at that time. I arrived back to pick them up from the 15:00 arrival and there were no gaps where cars had left in the meantime.