dunno, but it has both versions (on campaign IP missions ballistas are available, not sure if IP was in same time as campaign release)
on CB off they are even pretty OP (but not so much, considering its last tier unit, somewhat hard to get fast etc)
CB off vs ON:
same mana cost (2667)
health: 3689vs2400
a bit faster (0,9vs0,7)
Weapon
same AOE, reload time
but range xD
860 vs 650 (longer than cannoner :O vs longer than mage archer)
damage 1338 vs 900 + bad multipliers xD (0,5/0,75 on naval/fort type things)
x2 slower weapon velocity (760 vs 350)
from usefull unit but quite not OP*, they make it useless xD
*never played on multiplayer as, or vs Veruna without CB on, so its hard to say how look that unit with reasonable range