As far as I know, if you are staying at a DVC resort and are not a DVC owner, then the owner must book Magical Express.
If you are using points to stay somewhere like French Quarter or Caribbean Beach, since those are regular resorts, I am not sure, but you could call up the Standard Reservations department (NOT DVC Member Services) and try.
Of course, if you are staying ANYWHERE by booking directly from Disney (like renting a room), then you can call the standard reservations department and book Magical Expresss.