[ShannonA]

I haven't seen it happen and I suspect it's pretty hard.

I didn't get into the minutia of the rules, but if one player runs out of mana and the other doesn't, then he gets to push the wall a number of spaces equal to his remaining mana, until he runs out or it hits the other wizard.

So, you'd only have a draw if players both ran out of mana at the same time and the wall was in the middle (because if it's moved at all, the wizards still reset around it afterward).