Played a game today where situation 2 emerged. Ballista attacked the wall but it did not affect outcome of game so we did not bother to get an answer if it was ok or not.
After game my opponent asked a well know person in the community (no name needed) and came back with the answer that Ballista could not attack the wall.
This lead me to this Question:
Who can/can't attack the wall and why?
Taken from page 17MWC Ranged attacks may target a wall if either of the adjacent zones is in range AND LOS
Taken from Mage_Wars_Official_Rules_and_Codex_Supplement.pdf
In order for a creature to be able to perform a ranged attack against a wall, it must (1) have LoS to the wall
(trace LoS to the center of the border where the wall resides), and (2) be in range of at least one of the zones the wall borders.
This would suggest it's ok for 1 and 3 and not ok for 2 sins Ballista is not a creature. Seems kinda weird if so.