Naming would have alot to do with it. Plus most games use multiple roms files either all zipped together or in one directory. If you're trying to load a single BIN file, it might have all the individual ROM files combined with some sort of indexing system. MAME just wouldn't be able to read it.
Have you tried just changing the filename from BIN to ZIP? Chances are it's not that easy, but you never know until you try. I think you already would have been able to open them with something if they were just compressed, though. I'd bet it's a proprietary file format as I mentioned above with all the individual ROM files combined and containing some sort of indexing system.
There's no guarantee, however, that the contents of that BIN even conform to MAME naming conventions.