Its unlikely but not impossible. MpM fares are usually booked in N or X fare class, none of which are upgradeable using miles, though it never hurts to ask on the day as if VS are looking to shift people up a cabin if it is a busy flight then they may be happy to relieve you of miles or money. To upgrade, you generally need to be on an upgradeable fare class, so you *may* be allowed to pay the difference in fare to get you to an upgradable fare class, but dont count on it.
Take a look here for a further explanation on fare classes and upgrade ability, and keep your fingers crossed
Thanks,
Sarah
