True, they started the earliest work on the album after the tour but IMO they had nothing substantial (enough) until April 2003 when they called in Thomas (I bet most of 2002 was spent on the second Best of work).
What would be really interesting to know IMO is what happened between that time and this February when Lillywhite came in, all of a sudden. (and if there was more to that last fall visit from Lanois when he was on tour, then why didn't they change Thomas back then?)