I agree with Guy Betsy if the original poster were hoping for an op-up. However, it seems that he is hoping to be upgraded using his miles. If that were the scenario, then his chances are only there the flight is not oversold such that CX must op-up econ passengers to bus and occupy all bus class. In other words, chances of miles-upgrade would only exist if there are bus seats left after accomoding op-up passengers in case of oversell.