Passive or aggressive? Passive mobs can be led into towns with wheat, and bred outside towns and led inside. They can wander in, too.
No, I think there is a problem, I've seen them spawn in there (There is also both passive, and aggressive) It seems to be just Berlin.
Ok everyone. Do /region info berlin You will see there is no flag set to deny mob spawning in that region, why I don't know. Mystery solved.