All I could find is this:
"Your character can do nothing except maintain the hold, however. If he dedicates an action to any other effort, the target is no longer immobile. Your character still has a grip, but a successful overpower effort is required in a subsequent turn to immobilize the opponent all over again." (Pg 158)
It implies that if I do something other than Immobilize my opponent, the opponent is no longer immobilized. It also states that I will still have a grip. However, it does not indicate whether or not my opponent still has a grip.
However, in the next paragraph, it states:
"Successes rolled are compared to those that were gained by the holder when he applied the immobilization maneuver. If more are gained, the hold is broken and the victim is free again."
I don't know if this implies that the grapple is broken when Immobilization is broken, or if there is still a grip between the two characters.
Can a character break free from grappling completely after immobilizing an opponent?
On one hand, letting go of something is usually a free action, and both characters are still standing, so a move and attack is feasible.
On the other hand, since they are considered "grappling", you could rule that even after immobilizing the opponent, my character still has to disengage as an action before the grapple is officially ended.
Is an opponent who breaks free from being immobilized still "held" or is he "free" from the grappling?
I would expect that if an action is required to break a "grapple", then it applies to both situations.
I would say this is an ST call.
If you rule that an action is required to exit the grapple, or if you don't want to rule on this right now, can I just use my attack on the Green Man? He wouldn't be immobilized as Cory attacks, and Cory would lose the All-Out +2 bonus, but Green Man's Defense 3 is also ignored, actually coming out in favor for Cory by +1 die. Technically, the WoD rules state: "Damage opponent - Successes achieved on this turn's Strength + Brawl roll are applied as points of bashing damage inflicted on your character's opponent. Your character crushes, squeezes, bends or bites his victim." This bite is different, however, as it gets damage bonus dice and is lethal.