I read that City of Blinding Lights is a leftover from the Pop sessions, and the fact that Flood and Nellee Hooper are credited is verification. Same with Love and Peace or Else, being leftover from ATYCLB sessions, as well as Original of the Species which is obviously leftover as it appears in a TV segment which is 4 years old.
As for the rest. All it takes is a new set of lyrics, even a new chorus to change the name of a song. Who knows, Bulldozer may be on the album as something else, it's not out of the question.
I think there is an combination of new and old material on most of the songs, U2 aren't going to let good ideas die. Hell, if they had a good rhythm section or a good chord sequence or even a good melody, they would probably work on it, even if it's 7 or 8 years old.
One thing is for sure, they record A LOT of music during their sessions. I would guess they still have most of those tapes, maybe all of them and go back thru and find ideas. Some ideas don't work well with some producers, and some work very well with others. I'm not sure I could see them making Vertigo with Eno and Lanois. Lanois would be trying to pretty it up and Eno doesn't even like guitars, so he probably would have thrown some ambience in there.
I am hoping some unreleased stuff, real unreleased stuff is in that digitial box set coming out on I-tunes. I am guessing it's probably stuff that most of us have anyways. A real 'tracks' like box set might come out, but it will probably be when U2 calls it a day. Hopefully sooner, just not optimistic about that, I am happy they are stil making meaningful music in their 40's.
