The irish-folk scene in Vienna is not what ist used to be in the 80's but there are still some sessions in several pubs. You will find a lot of irish pubs, but the music is not always irish (not even folk). The only irish group visiting Vienna are the Dubliners. In Vienna you will find a lot of blues or (even more) jazz-music. If you are looking for events try the following sites:

www.weltenklang.at
www.tradivarium.at
www.cafeconcerto.at
www.euroots.com
www.blues.at
www.bluesimon.at
www.bluesconvention.com

Don't expect too much

good luck Erich