From some posts in rumor sites, it looks like companies routinely patent such designs, and sometimes even if they have no plans for making an actual lens out of it. I believe I have seen a full frame design from Olympus, who keep stating that they will not go that route at all! In the example of Sony and Canon having identical base design, they could both be licensing a design from a third party!
Niels
Is it possible to patent a third party design?