I got an xt:commerce running with multishop configuration. It runs on an AWS wich has hard links on file system to simulate 5 different shops. What I am trying to accomplish is that if you log into one of those shops - you're logged in in all of them. How could that be accomplished?
In order to maintain session across domains ... you will need to use same session storage and subdomains to have multiple shops. You will then need to configure session cookie to be shared acorss all of those sub domains.
You cant share session cookie on different domains just using cookies. You will need to manually link session data through GET variable and then manually re-create session on the destination domain.
Share Session Between Two Websites might help.