Why can't you believe that people would buy D1 seats on a transcon? They do all the time. That said, I highly doubt any agent would tell you how people cleared into J (paid, RUC, whatever). The only thing you can do is call DL once in a while to ask about whether any seats have opened up for RUC upgrades, as sometimes RUC's aren't coded properly and you have no way of knowing whether yours was or wasn't.