i'll bet most of the large frameset manufacturers offer their clients (the small bicycle manufacturers) enough options to easily customize their clients framesets to the point where they are not identical. and then most of the larger ones demand some, if not all, of the design specifications to come from their designers.

i think some of the recently purchased 'old school' brand named bikes, like motobecane. dawes, mercier, and windsor, use some of the same frames... although i won't put of much of a defense if someone challenges that statement.