I've checked around but haven't really found a clear answer to this.
I note from experience in the OC that NPCs use potions as part of the AI scripted talent behavior; for instance
tUse = GetCreatureTalentRandom(TALENT_CATEGORY_BENEFICIAL_HEALING_POTION);
if(GetIsTalentValid(tUse))
{
//MyPrintString("TalentHealingSelf Successful Exit");
bkTalentFilter(tUse, OBJECT_SELF);
return TRUE;
}
but this is about the only evidence I see that NPCs can activate any kind of item at all, and this bit of scripting is, eh... cryptic. Seems like something is hardcoded from here out, and the whole process of activating an item cannot be scripted.