A bit late, but
ffxiii.net shows latest FFXIII info from Famitsu, and it has more info on the battle system. From the look of things, it seems that there are general AI classes that you can set characters to; classes listed so far include "Attacker", "Defender" and "Blaster".
Frankly, if you're going to go the "AI controlling your teammates" route, I don't see why they're going with this system over the already-established gambit system, except maybe to placate those who thought the Gambit System was too complicated. Or perhaps they
are using a gambit-like system, only with specific macros for different AI types. Didn't they say that the more you played the more control you got over your character? Perhaps as you increase level you get to fine-tune your AI options a la gambits, but at the onset, the scripts are fixed per AI class.
Oh course, I could be completely wrong. Perhaps when someone translates the text we'll have a better idea of what's going on.