Duc de Guise wrote:
3. A tank in an empty hex could spend MPs turn after turn to stay in motion within that empty hex whilst not leaving it (i.e. to make it less likely that ranged shooting attacks can hit it).
I don't have the rules in front of me ATM, but I remember having read that you must move at least one hex to stay in motion.
EDIT: Now I read the rules again. Last paragraph of 3.3.2 says: "A mobile vehicle may always move one hex () by expending all its MP () to do so and then remaining in motion ()."
Not exactly what I remembered. But I understood it this way.