Ultan Cowley, author of 'The Men Who Bult Britain' has done a considerable amount of work on the Irish Navvies, and might be able to help. He has just completed a second book. He has posted here on several occasions.
Some years ago we attended a conference in Aberdeen; one of the papers was on the influence of the railway navvies on the North East Scotland song tradition which, the speaker (I think, the late Peter Hall) claimed was extremely significant.
Jim Carroll