The P Club site states <<Presidents Club members must be ticketed on a Continental flight to gain access to international affiliated lounges>> but doesn't specify if the same applies to those who qualify via ST Elite Plus status.
But you are not missing much anyway - in addition to being at the other end of the terminal from the CO gates, the offerings are pretty basic - coffee/tea and some booze, a few unimpressive snacks. There are wireless and a couple terminals to use, and some places to sit but no work spaces. The Upper Deck was closed wen we were there yesterday, no reason or expected duration of closure. Overall feel is more like a coffee shop than a club (of course I may just be spoiled by the great P Club product )