the nice thing about fireworks is that the fileformat is a viewable PNG when opened by someone without fireworks, so process files are visible by everyone involved.
i reckon we'll get to a point where early in a repo's life there'll be a concepts/design folder with process files - would also make sense to plan the architecture in the same fashion...hmmm the possiblilities
so that the dev planning the models/views can collaborate with a front-end designer as to the architecture of a site, but all within github etc etc etc. i can but hope.