Andy, what's the reason for the question? is it because of cable lengths etc? Unfortunately HDMI doesn't allow the type of communication that the USB would, HDMI allows basic I/O commands i.e. power on / power off (if you have an amp connected with a TV etc and HDMI command is set to on, it will control the power status of those devices)
The only option you've got is tethering with USB using the canon software for live view if that's what you're on about using with a HDMI monitor attached ?