I was playing a LotR game on the Minas Tirith and Pelennor Fields maps combined. The trebuchet mechanic, I think, is inspired.
Some questions arose:

1. If the character taking the power action to use the trebuchet has Battle Fury, can he make the PW attack? The judge ruled they could, because it is a free action. But afterwards, I realized, by that logic, a fig with BF could use Running Shot to take a ranged attack.

2. If there is a piece of blocking terrain (Barrier) marker in the target square, can the attack be made? The rule of occupancy doesn't matter, since the target square can be occupied by a character, but would lines of fire be able to be drawn from a square of blocking terrain?

1: no since he can't make a ranged attack and PW results in a ranged attack.
2: now that I've reread the rules I'm not so sure.
Used to be that the square you occupied did not effect your LoF but that wording is no longer in there. So i would have to say that you would not be able to draw LoF since it is blocked.

1) No, because:
2) The only time terrain is not effected by standard rules for Line of Fire is if it is Hindered.
So the shot would be blocked.