Why do Colon, Nobby, and Dibbler remember the altered timeline at the start of the book, before the storm? Alright, so it's perfectly possible that the original Keel promoted Colon and bought a pie from Dibbler, but the spoon has to have been Vimes. Keel wouldn't have recognised Nobby, and given that he apparently didn't attract Madam's attention and wouldn't have made instant enemies of Coates and Quirke the way Vimes did, Nobby probably wouldn't have been following him in the first place.
Chalk it up to time travel.
I don't see why Keel wouldn't have attracted Madam's attention. We never get to hear the real Keel's story, but he was apparently pretty awesome, and just as involved in the revolution as Vimes was. Like when every other Watch house was attacked except Treacle Mine Street, the only difference in the timeline was that the riot happened in Dolly Sisters instead of Morphic Street. We don't know if Keel pulled the same thing that Vimes did, but there's no reason to assume that what happened was wildly different, in the actual timeline it seems that Keel still prevented the Watch house from being attacked. I don't think Vimes did things all that differently, so he still would have attracted Madam's attention and Nobby would have been hired to spy on him. He probably wouldn't have made enemies of Coates, since Coates did actually know him before, but overall, I think that Colon, Nobby, and Dibbler had roughly the same experience with Keel as they did with Vimes.