Bug/Issue AI won't use transports

I'm currently trying to build a map where the AI uses barges to send units across a river to attack the player, but no matter what I do, the AI doesn't use the barges. I've tested it by setting the control of Player 2 to Human and doing it myself, and it works just fine. I've also changed the AI play style from "Balanced" to "Aggressive," which also had no effect.

Some googling tells me that other people have been having the same issue for over a year, and that even AI players in official missions don't use any wagons, balloons, or barges.

I'm really bummed about this, since I had some fun ideas for missions based on defending against transport-based naval attacks. Can we get this patched?