If you were to type streets of derry in the "Digitrad and Forum Search" page on the main Forum page, you would get a short list of links to previous discussions of this song.  One of them would be this:  RE: Tune Req: The Maid Freed From the Gallows  which has a long list of relevant links.  None of them include the full set of words used by the Bothy Band, though there is some discussion of those lines that Triona sang particularly indistinctly.  Some interesting background reading for you, at any rate, which may perhaps help you to work the lyrics out yourself.

Malcolm