Good point; the more I think about it, the more I wonder if Civ5 has one generic AI that, instead of being governed by variables in an XML file, simply plays to its advantages/disadvantages. If it does, it'll be great for keeping the game interesting (no more knowing beforehand exactly how the AI will react in diplomacy/war), and it'll be a godsend for modders. To create an interesting new civ, they'd just need to give it a good ability/UU/UB, and the AI will sort out the rest (e.g., a mod civ that gets a bonus to research when in a research agreement will be quite the diplomat, and one that gets a SP discount will shoot for Utopia wins); no more tweaking modifiers in newciv.xml until the new civ acts right.
There's no doubt the AI is governed by XML-values. UU/UB/SA is far from enough to create a "personality".
I very much doubt Monty will even think "Hey, my ability encourages me to go to war". Instead it will be "The XML tells me to declare war" and then the gained culture comes as a result of that. Same goes with units. If the unique ability needs an alternative usage, they will probably not be able to exploit it. The XML will tell them to favor the tech and the unit slightly higher than normal, but any advantages they get is just pure luck.