The value of the DTStudy threads: The Irish Independent quote gives Robbie McMahon as receiving the song from the author's nephew (John Considine).
The writing from Frank McGrath gives it as received by Robbie McMahon from Moira Keane, and with its authenticity verified by the nephew of the author.
It is not stated what the relationship was of Moira Keane to Michael Considine, but as the aunt of Michael Considines nephew, it is possible that she was his widow. (possibly going back to her maiden name)
Martin Ryan may be seeing Robbie McMahon shortly, and may be able to confirm the details. But, as with the aural tradition, it may be that the story of the 'provenance' of this song has been embroidered over time.
Now is probably he best time to try to nail down any available facts, as the longer it is left, the more nebulous those facts become.

I am not trying to question anyone's version here, merely pointing out that we appear to have two, contradictory, stories coming from almost primary sources!I look forward to reading more of the saga here.
Nigel