It's custom map. Blizzard's default AI won't work as you want them to, in such case.
You will have to trigger/create your own AI ;> Basic AI tutorial (at the bottom of Av3n's tut there are additional 4 helpfull links to other AI manipulations).
the .ai file is in the Imported Files so it can be viewed. and he also have the map's custom AI in the AI editor. i don't really know what's not working; i saw the AI harvesting trees and goldmine, but i'm not sure if they are training any troops. is that what's not working?
i don't know if this has anything to do with the AI not attacking the base (since the AI's race is Naga and it can actually traverse through water), but I read somewhere (i think it's in the Tutorials section like Spinnaker's link, too) that an AI will usually move to its location via a land path. if there is no land path (the location is in an island, or maybe bounded by cliffs) the AI will think it is unreachable, and that also an AI cannot use airships. try placing a Way Gate. i saw in several melee maps that AI actually use them.