I installed hub and git via Boxen on OS X 10.8.3. I'm using oh-my-zsh.
Pressing Tab after git cre, there is no auto completion. There are only git zsh completions.
$ which hub
$ which git
git: aliased to hub
$ hub --version
git version 1.8.0
hub version 1.10.5
zsh: do you wish to see all 137 possibilities (137 lines)?
Unfortunately, this is known. #295 #231