There are a few of us who arrange and play irish dance tunes in campanella style, with the uke tuned in reentrant C tuning. Often we transpose down two half steps from the key in O'Neills or wherever we found the tune. If you hunt around on the forum, you can find links to tunes by Jonathan Lewis, ukuleletim, and me. In addition to Ken Middleton's ebook, there is a good collection of irish dance tunes by Rob MacKillop published by Mel Bay. Also Sam Muir has a new book of Scots trad music arranged for uke, published by Schott. She has some samples on youtube - very nice, in my opinion. All of these arrangers work exclusively in high G. I know there are also some low G arrangements out there too.
I haven't seen much on the uke as a rhythm instrument for irish trad music. I am sure you could accompany vocals on traditional tunes. Probably it would be quite nice. And there is surely a way for the uke to play behind session instruments. But the uke isn't as loud as a fiddle or a box so I'm not sure how the little fellow will be heard. As a rhythm instrument I suppose you could go either reentrant or low g.
By the way, I share soundbored's love of irish music on banjo. In addition to Angela Carberry, I like John Carty's banjo and tenor guitar versions of irish tunes. When I arrange irish music for the uke, the banjo sound is my model.
Let us know what you find...