Ok, i tried the version from here http://www.shacknews.com/file/12204/command-conquer-red-alert-soviet-disc/ and it comes with a folder called xp patch, not sure what version this is but i think its the EA one.
Yes the ai does ally back, and you can force fire on them and they wont respond untill you un ally. Heres a short vid i made, please excuse the choppiness as i made it on a slow fanless laptop : Red Alert - ally with the ai Basically i ally right away and then take over his buildings, and the other computers come and smash my base. You can tell they are allied with each other because they attack in unison and don't fire on each other.
I Also attached the patch notes if anyone cares to know.
PS i think its cool that people still play C&C after all these years...
patch_notes.pdf