Not in the manner that H.sie's Wolfpack addition in SH3 does, but the game does "call" for reinforcement assistance when it is available nearby, especially if you do a "Contact Report" in the "proper" manner (what, after all, is "proper" in this game??). I don't have my install available on this computer, and I do not recall if there are "embedded" AI subs in some of the convoy groupings nor if there are AI submarines by themselves, but your supposition that "they simply walk around in their zone" is probably correct.