If you look at the thread here about mixte bicycles, you'll see many with centerpulls mounted to the center stays. Others with sidepulls mounted in "reverse pull" to the top stays. As noglider pointed out, I, too, have seen them with pulleys, but couldn't see them on your pictures.

It's a really neat bicycle, I'm just curious about differences from what I've thought to be status quo.

Nice blog, too. I've seen it before, but don't routinely view blogs.