I read on RPGamer.com that the music will be primarily by the Tactics guy, and Uematsu will be responsible for only one song, but it will be a major theme.

If it's anything like the film industry and the soundtrack techniques they use there, the theme Mr. Uematsu composes will probably appear here and there in all sorts of spots around the game in various forms.

You know, like a dark and sullen version for when the villain makes an entrance. A brighter happier version of the theme for Vaan's first journey via airship. Something like that. And then the Tactics guy covering the rest. I don't know if you all played Tactics, but that music was really pretty good, considering.

Considering the fact that the game was entirely text-based, and the story scenes were all in game-engine. With limits like that, it's next to impossible to score emotional scenes with any timing.
But since XII is going to be voice-acted (and probably cut-scene heavy) the composer will really have a chance to shine with oppotunities that weren't previously available to him in earlier projects. I think it's looking pretty hopeful.

I hope I cleared up some confusion.