That's crazy! I have an Australian Cattle Dog and we joke around about her being miniature because she is so much smaller than other dogs of her breed. I couldn't imagine her being Chihuahua size. First off she's a herding dog. It seems like a crime against nature to make such a hyper, working dog teacup size. It just seems uncanny to me. Very interesting though, it'll give me something to think about.
I was looking into getting one at one time. They get to about 20-30 lbs if I remember right. They call them Northamerican Shepherds or Mini Aussies I believe. It was awhile ago so I do9nt remember correctly.. sorry!