Update...I've been able to curtail the attacks by watching the Aussie after meals, games and treats and recognizing the "look" as she approaches the BH, and also the BH's posture and demeanor (i.e., he can tell what's coming). As she approaches him I tell her "Be nice!" which distracts her; and I tell her again, and again if necessary until she's relaxed and whatever demonic urge she might have has passed. Hopefully by breaking the habit she'll eventually forget that she ever did this. In the meantime though the poor little guy scarfs down his food and then runs and hides, even if it means leaving food in his dish if she finishes before he does.
Otherwise they play and roughhouse a good part of the day, with the BH giving as good as he gets - which is part of what makes the attacks so odd. I don't know how they can run around, wrestle and play tug-of-war all day and then assume attacker-victim roles only at specific times. Talk about a toxic relationship...We're still hoping to either locate his people or place him soon, so maybe he won't be scarred for life.