Well, due to the lack of response, I'll tell you my closest (non-G15) setup that has worked for me.
Using an old Minolta DiMage 7i, I've triggered my Phottix Strato II's, via PC sync cord adapted from the camera's hotshoe. That camera maxes out at 1/2000 on manual, and was triggering an old manual flash attached to the Strato receiver. Caught the flash in frame each time, and because it's electronic shutter, full coverage. I had the same success triggering the remote flash with an optical slave using the built-in flash ( 1/16 manual, as any TTL type pre-flash will pop the slave too early).
The old flash may have a fairly long burn time -- I don't know and don't have the tools to measure it. I didn't have my 580 handy, but if you are interested, I can redo the test with it on lowest power (shortest flash duration), to see if they still sync. It's my understanding that studio strobes are generally slower (the light is on for longer) than speedlights, so I think in this case, it may be a benefit, if the timing isn't exact.
I don't think there will be much issue having your camera trip the triggers. If it'll fire a canon flash, it should fire a trigger. Actually, delay that. Googling found this about the G12:
http://www.flickr.com/groups/1088996@N21/discuss/72157628714843327/ Possible pit-fall #1, (at least with a possible solution).
I think the other pit-fall would be around any delays introduced by the trigger. At slower shutter speeds, there is clearly a longer window during which the flash pulse can happen. The faster the shutter speed, the smaller that window. If the trigger system delays the 'flash now' signal long enough, your flash would fire after the shutter is closed.
Failing someone posting info with your exact setup, my suggestion is to find a G15 somewhere (friend, store) and introduce it to your triggers and a speedlight and try it out.
