I don't know for sure, but it seems like AI vs. AI alliances seem to be a little more realistic than AI vs. Human alliances (which the AI often has no problems breaking at any time). Doing test runs I am fairly happy with what the AI vs. AI diplomacy is doing in EB so far, but I'll admit that when I do play RTW the whole alliance thing does get me irritated too. I don't know what can really be done about it. There may be some guys in the mod who do have answers, but I don't know what they'd be and I'm not particularly optimistic.