I wonder, in the case of "Grand Bosco" and "It Happened To Me", if one wasn't an alternate take of another. After all, if it was, Iry would have only gotten paid for the one song. But then again, I believe one of them came out after he was dead.
I did speed up "It Happened To Me" and it the pitch and the speed prety much matches "Grand Bosco", which is why I'd question if they were both cut at the same session.

I think they are different recordings of the same song.

In Grand Bosco, he says Si tu me voir 'pres marcher gone a Grand Bosco.

In It Happened to Me, he says Si tu me voir 'pres marcher au long du chemin d'fer. He doesn't mention Bosco at all.

In Grand Bosco, it's after verse one that he tells the fiddle to take it. In It Happened to Me, it's after the third verse.

Most bands you hear today mix up the two sets of lyrics very happily. They are very close.