it actually doesnt suit IE for rota/industrial relations reasons. the trains are all limerick based, you would have to get a train to work its way to BB at an insanely early hour of the morning so it can start off at about 6-630 from BB to get people into Limerick for a proper time.
if you are going to use Laois Train Depot trains it means a 22k and they will mash the track from BB to Nenagh into the ground fairly sharpish if running four times a day on it.
Weather of not it suits IE the NRP want a Dublin service and I can't see them settling for anything else. BTW 22k on all services would be a blessing.