M3R1IN you might want to take advantage of any offer to be flown in and out of remote areas, as theres a better chance of finding stuff where its hard to get at.
Also, those involved in prospecting for larger companies sometimes know of deposits that aren't economical to actually mine by those companies. In deciding what areas to mine, large companies and even some of the more skilled small scale miners are looking at a site based on cost to access and work, along with the number of man years of labor needed to work the site, compared to the expected returns for all this.
If a site easy to get to, but only offers say 20 man years of labor, then sending crew of 200 miners in to clean it out, isn't very practical as it would be tapped out within a couple of months. Just something to keep in mind if you run into people in the field of claim staking.
I don't know of any pay-to-mine places in BC, but there are free to pan places known as "Recreational Panning Sites". The following page has maps available for download in Adobe pdf format:
http://www.em.gov.bc.ca/mining/titles/Panning/Rec_Panning.htm
Heres a quote from that page:
"Recreational panning is restricted to hand pans, hand shovels, and metal detectors. The use of sluice or shaker boxes, suction dredges, and other mechanical devices are not permitted."
I don't know about the Stewart area, but the Frasier river at Quesnel is one of those areas where you are free to pan or use a metal detector.
Having never panned south of the border, I really can't say how you would do in California. I have seen some good sized nuggets come out of northern BC in the Atlin lake area and from the Yukon side, but you really need to be equipped for anything up there, (including bears). I hope to go up that way myself within the next two summers, depending on how things go between now and then.
Good luck.
F.