This is the result of a quick HDR time lapse test with my G12. Picked up my "Aputure Timer Remote Control" yesterday (40 USD/Amazon) and tried out timelapse in combo with the HDR feature. Would have loved a more contrasty scene for this, but my initial impression is that this works quite well. A couple of issues that you should be aware of: The HDR option resides in the SCN-setting on the G12 with most settings fixed (automatic). The HDR image is processed in camera and takes several seconds, meaning that you cannot get a shorter interval than 10 secs (roughly).
Aputure Remote: amazon.com/Aputure-Powershot-Compatible-Inexpensive-Intervalometer/dp/B003Y35VJA