In Donegal, Tom Munnelly claimed that a man called Terry Moylan had asked him about this song some months ago and he had dredged it up from his memory.I finally caught up with Terry last night. He says he has been slowly compiling a book of Dublin songs (Yes! a rival to Frank Harte)and remembered hearing Tom singing Billy O'Shea many years ago. In fact, he insists Tom wrote it. The "Rogerson's Quay" reference is to a pub they used to drink in many years ago. Tom, meanwhile, is tolerably vague on this theory.
I suspect its true.
Regards to all