Depends on its orders. If it has been given the "remote deploy units" order then it will. If not, it might take a while to get around to actually laying the minefield. You will next ask "Does the AI use the 'remote deploy units' order?"
I think it does, since the AI is (supposedly) designed to get things done as simply as possible. But maybe the mechanics of the code are different from the AI side? So, I can't really say since I have no direct experience with this situation. You'll have to wing-it and see what happens. Just remember that the complete turn of each player (AI or otherwise) is executed sequentially. Even in "simultaneous move" mode the rest of the turns (like dropping mines) are sequential. You do possibly have the advantage in Simul-mode that your ship could arrive BEFORE the other ship if it's closer, though.
[This message has been edited by Baron Munchausen (edited 28 November 2000).]