Somewhere in here I remember someone on the DFMOD team mentioning having trouble getting mouths to move while a character is speaking. I myself do not yet know the answer. However, I just played an old mod made by a Mr. Jake Keating. It was the Colleseum mod for JO. In it, the characters' mouths move when they speak in cinematics.
I figure you guys might be interesting in asking him how he did it. His website is http://www.jakekeating.com
If you find out, please share the wealth :-)