Well the least Irish Rail could do is provide the direct link
http://www.translink.co.uk/SpecialEvent.asp
Note NIR have 3 specials for both 6 nations games and they are on sale now, they always run 3 specials
The good news is Irish Rail have killed the dedicated special train in favour of adding the specials into the normal timetable, the passenger choosing from the entire timetable. Student, weekender and farecards are also valid