Is there an "AI" component to this game? I'm in a game that just started, and immediately after the start, a player near me resigned. I figured this was a lucky break and I could grab the empty outposts between us with no resistance, but now I see subs from the resigned player headed to these outposts. The rule book says elimination cancels all future orders, and resigning is a form of elimination, so it can't be an order from before the resignation. Does the AI launch for resigned players?

There is no AI implemented into the game. The resigned player probably had subs headed to his own outposts (then resigned) but you couldn't see them because they were outside your radar.

But they aren't headed to his outposts, they're headed to the empty neutral ones at the start of the game. Is it a bug?

No. If he sent them before he resigned, then they continue on their current path.

They resigned in the four hour window between when a game is full and when play starts.

I don't think orders issued to happen as soon as the game starts are considered future orders, so they would still be issued.

Hmm... That doesn't make much sense, but it has to be what happened.