He's probably running an earlier version of TMO, or somehow reactivated subron 50 in TMO.
Subron 50 is an atlantic squadron of fleet submarines that was stationed in roseneath scotland. (6 gato's and 1 tender to be exact )
Info on that here:
http://www.subvetpaul.com/SAGA_6_98.htm
I deactivated it because.
a.) People were getting new commands of gatos and getting sent to scotland instead of pacific bases.
b.) I didn't have enough time to do the campaign right. It was a larger project that i realized at first, and i got over ambitious. What i had was rather barren, and not really worth spending time playing.
The files still reside in TMO, they just aren't active. I deactivated it by starting and disbanding the squadron before the US entered WW2, so its "predated out" of play.