Situation: an ally stands in a hallway, between you and an enemy, and adjacent to the enemy's square. The only way to reach the enemy is through your ally.
Can you Bull rush the enemy?
BULL RUSH rules state:
"You can make a bull rush as a standard action or as part of a charge, in place of [a] melee attack...If your attack fails, your movement ends in front of the target."
For comparison, the OVERRUN rules state:
"As a standard action, taken during your move or as part of a charge, you can attempt to overrun your target, moving through its square....If your overrun attempt fails, you stop in the space directly in front of the opponent, or the nearest open space in front of the creature if there are other creatures occupying that space."
This wording seems to indicate that a Bull Rush may not be done through an ally (since you can't charge through an ally), but that an Overrun may (since you may move through an ally and do the Overrun as part of that move).
1. Am I interpreting this correctly?
2. What would be the reason that one would work differently from the other? [Something to do with the AoO's provoked by Greater Bull Rush, maybe?]
I'm leaning towards a house rule that makes Bull Rush read like Overrun in the two relevant sentences, but wanted to get feedback first.
Bull rush is a bit more powerful than overrun. It doesn't have a way to dodge it like overrun does and can shove people into a new square of the attacker's direction and possibly hurt the target and/or anyone into which the target is shoved.
That is why I imagine bull rush is a standard vs overrun's move action. Based on that, I'd say that you are correct. Both can be done as part of a charge action, which means they are bound by the rules of a charge and thus can't go through an ally's square.
The bull rush may also be done as a standard action against someone next to you; basically stiff arming them. You can still move through an ally, stop next to an enemy finishing your move, then taking your standard to shove. Nice thing is that if you start next to an enemy, you can bull rush and then move away.
The overrun may be done as a standard action as well, but at any point during a move. You walk a few squares, pass through an ally's spot, then when you get to the enemy you declare the overrun and keep on moving. You choose to use the standard at any point of the move (so I interpret). Unlike the bull run, you cannot overrun and then take another move action since you've used both actions at this point.
So, really, it is moot. The reason you do this with a charge is for the attack bonus. You can't charge through allies. You can move through them, but you aren't doing either maneuver for the duration of your movement, just at the point you choose to activate it.
You don't have to charge in order to bull rush. Doing a bull rush in that scenario wouldn't work without the Spring Attack feat, though. That's the houserule you'd have to allow. Spring Attack combined with other standard actions besides a single melee attack. You would have to spend at least 5 feet of movement to stand in your ally's square, then attempt the bull rush. That's normally your whole action, and you would end your turn standing in your ally's square, which isn't legal (unless he's prone or unconscious). Spring Attack would allow you to then move into the newly created square between your ally and the enemy.