Most mods use AI uboats patrolling
GWX does for sure - this one passed me in BF36 the other day when I was heading for patrol grid
BUT
Am not sure even if you send a radio contact whether they come or not
I always send a contact report when watching a convoy and apart from the Lolwaffe if close to coast nothing has shown up
And then as Dietrich rightly says the AI would be limited if did turn up as surfaced
Sure they would have the surfaced speed to get to you but wouldnt last long
Submerged AI units would only be of help if right in the convoy path as slow speed
Tis a pity the wolfpacks were dropped in development as time closed in