Based on the above, the AU magic system can be dropped in nearly wholesale, and will represent the various "wizard" traditions of taladas quite well. (Better than the 2E magic system the world was designed to use, in my opinion.) Of course, since one of the premises of the campaign is that Culture Matters, the classes won't be evenly distributed; different societies will produce different spellcasters. But I'll get into that when I get to classes.
Clerics are a problem, though. Certainly, the setting material implies D&D Clerics. So there are two real options. The first is to just drop clerics intoi the setting; while that sort of defeats the point of using AU, they'll be rare enough not to worry about too much.
The other option is to adapt. For this to work, the DM has to accept certain premises.
Premise #1. The gods don't necessarily empower all their servants in the same way. While Ansalon has clerics, Taladas may or may not have different divinely empowered folks.
Premise #2. Priests being super-healers is primarily a Mislaxan thing. This can be argued both from the setting material (as it's only in reference to the mystery cult of Mislaxa that clerics as healers is mentioned) and from a rules standpoint, since many of the other gods in the Time of the Dragon boxed set had only limited healing capability, if any.
Premise #3. Healing hit point damage isn't that big a deal, unless you're part of an adventuring party. For an adventurer, it's vital to have someone handy who can patch you up, but on a societal level, that kind of wound tends to take care of itself, one way or another. (Either you heal, or you die.) If you have a secret society of wandering healers, you really need them to take care of lingering ailments, diseases and the like, instead of hoping there's one nearby when you happen to get thwacked with a sword.
The hit point healing spells in AU tend to be simple, while the spells that treat disease and the like tend to be complex or exotic. To me, that means that the fact that the local witch can cast lesser battle healing doesn't reduce the specialness of the wandering Mislaxan priest, since the priest can cure the plague and the witch can't.
Therefore, here's what I'm thinking about clerics. The average deity's empowered servant is a Champion, with a cause tailored toward the particular deity. Empowered members of the mystery cult of Mislaxa (I should really start abbreviating that) use the Greenbond class.
Still, I'm not settled on this, and am open to suggestions.