awesome! when i brew install though, it fails to find libusb-1.0 even. so then i brew install libusb, and it tells me libusb-1.0.9 is already installed. still can't get it to "see" that libusb is already installed when i attempt to brew cgminer.
Try running "brew doctor" and seeing if there are any errors or warnings. Fix any you can. Also, make sure that "/usr/local/sbin" is on your PATH. I had to add the following to ~/.bash_profile:
export PATH="$PATH:/usr/local/sbin"
I just tested and I am able to build with --enable-modminer using the libusb installed by Homebrew (1.0.9).