I created a subdirectory and put a mirrored file in it. When I tried to migrate the mirrored file to another MDT, it returned an error migrating the mirrored file that I didn't expect:
So it seems like the directory was migrated, but the mirrored file was not. Is there some reason that the mirrored file could not be migrated? I don't think that should be any different than migrating some other composite file.