It is a really weird sport in Ireland, firmly a Protestant sport when I was growing up so one I never got involved with in any way.
It is still undoubtedly ‘posh’ in Leinster but only in the realms of school rugby which holds a sense of self-importance to be utterly bizarre to anybody who did not attend of those schools. Brian O’Driscoll tells a story of being out in town for a few pints one night and getting verbally berated by some dude on the basis that said dude had won a Leinster Senior Cup with his school and BOD had not.
Thing is with our dominant current position in world rugby and the inevitable World Cup success in the Autumn the sport is now hugely popular. I have neighbours, ordinary chaps, who attend matches and who will discuss rucks and mauls (I suspect they don’t know the difference) while only last year I had to change my football team training from a Wednesday to a Thursday (having been Wednesday for years) because 5 of my team had decided to take up the foreign Protestant sport and there was a clash.
Certainly it's the case in Leinster that rugby is dominated by the big independent schools. Like BOD, my dad went to Blackrock College, where rugby was virtually a religion. Clongowes, St Mary's, Belvedere et al are similar.
The anomaly in recent years has been the rise in Munster rugby, of course. In the old days, Irish provincial rugby was exclusively dominated by Ulster and Leinster, but not any more. Now I don't know the backgrounds of the Munster players, but my instinctive assumption is that people from Munster all work on farms and eat their young - hardly 'posh' in other words.
Also, you realise that football was codified in British public schools and is therefore just as foreign and protestant? ;_)