It has been my experience as well that Elite status is a major factor in standby list priority, for boarding and obviously for upgrades. Given that CO allows Golds and Platinums to book a seat on a "full" flight ("Guaranteed Reservations"), one would assume that they also take status into account for standby priority. The Presidents Club representatives at SFO have told me several times that my Platinum status would put me near the top of the list, and I have never missed out, as a Gold or a Platinum.
-Adam