I've yet to do the battle for bunker hill, having done only 3 main quests i believe i'm a ways away from it, however i'm doing my thing working on settlements and I go to quick travel to the next on my list and that's when I notice the map shows a supply line running between Bunker Hill and Tenpines Bluff.

Question is, is this a bug or is this meant to happen? I thought perhaps as you build up more and more settlements Bunker Hill, being the defacto heart of trade caravans, automatically starts sending out caravans to your settlements, even before the quest req, the req needed to actually build there.

edit: another one just appeared, it would seem it's automatic, and i think it's based on the number of settlements you have chained together, just an fyi for those interested, all the guides i ever read about settlements never mentioned it.