This may be a little too late, but newjack might appreciate a few pointers to three multiplayer missions with AI players present, since that information is a little obscure (and entirely obscure if you rely solely on the info in the Outpost 2 multiplayer level selection screen):
Two Last One Standing maps included with the OPU Outpost 2 package have AI players, check: La Corrida and Peacekeeper. Both are Eden AI players and defensive in nature - they will not initiate attacks against you, and you're still an enemy with the other player, but you can work together to defeat the computer bases and agree to call it a victory when the computers are eliminated, if you like. Not much replay value with a purely defensive AI, but the option is there at least for a little taste.
If you want some real fun with an AI player though, the best one included with the download from this site is found in the Space Race section, check Caught in the Crossfire. Fun level where you start the game packing up to escape the blight which will wipe out your base in a few days. It features an Eden AI that produces increasingly heavier armies to attack you and your allies while you try to build a spaceship and escape. If you're really good you might even manage to take out the AI together, but it is pretty well defended. Countering the attacks while building a spaceship and trying to keep the blight at bay with walls is quite entertaining.
I don't know of any other included levels with AI players to do battle with. It is unfortunate that the Outpost 2 developers didn't put a bit more work into the multiplayer aspect. So much wasted potential, argh! But considering Op1 didn't have multiplayer, I suppose we're lucky Op2 does at all.
Hope you have fun with those.