Nobody on this island would like to see "Maedb" back in traffic more than me! But I have to say (and with benefit of RPSI experience for many years) that it is safe to say it won't run again.
Theoretically, of course, it could; theoretically anything can happen. The issue which would need to be faced are the size of the locomotive, which would make many bridges tight, the colossal cost of retoring it and training crews, and the economics of running it. The RPSI operates in a much smaller marketplace than UK train operators, and even if the market was there things like platform lengths come into play. How many stations in Ireland could take a 15 or 20-bogie train? Modern H & S regulations wouldn't allow a train to operate which was longer than the passenger platform at which it stopped.
Cultra have a live steam model of 800, though not on display. It is one of a number built by the late model maker from Dublin, (someone) Montgomery. I think it is 7 inch or 10.5 inch gauge. THAT could operate!