Speaking as an Irish musician in England, I still travel back to Kilkenny each Summer to play in a few sessions. As far as Kilkenny goes I can vouch for them being very real indeed. The Monday night session in Cleere's Bar there has been going non stop for almost 30 years now.

Almost nothin is ever formally arranged or set up re the session. The musicians, singers etc simply turn up and certain seats are always there for them. There are the instrumental only sessions,and as in Cleeres instrumentals interspersed with local and visiting talent, songs, stories, poetrty etc. Usually very lively and late finishing. Can be noisy too so don't expect UK folk club type reverence, basically if you're good enough they'll listen. Sadly central dublin these days rarely sees a real genuine session