In this case, the troll will win when controlled by a human player. By retaliating against the titan's attacks and skipping its own turns. Or, if the titan skips its turns, the troll will attack it at the end of the round, receiving a retaliatory hit but immediately recovering.
The cart doesn't play a significant role here. If the difference between attack and defense is 3 or less, the troll will win anyway. If it's more, then over a large number of turns, as the troll attacks the titan, the titan will likely, at least once, deal damage greater than 40.
You can test this on my experimental map.

