I created a couple of sound files and successfully set them up in a mission. I am able to "playSound" them, as well as use the "say" command to get a unit to produce the sound. I also used Wave2Lip along with 16bit mono .wav versions of the sounds to generate .lip files for use in lip syncing.
The lip syncing does not occur, although the .lip files appear to have been generated successfully and the sound does play.