I just did a test...
Also applied my method of pre-creating the facial animation (of talking and head motions) and THEN importing the BVH to hip.
Walk designer BVH did not add keyframes to the Head/Neck, so my lip-synch head-motion was uninterrupted providing the effect I wanted, awesome!!!

Also Fingers are also clear of BVH keyframes (but not hand motion) so you can pre-animate the fingers (clenched fist, curl fingers and thumbs) without worry.

Carrara 7 Pro, Anime Studio Pro 8, Hexagon 2.5, Zbrush 4.6, trueSpace 7.6, and Corel Draw X3. Manga Studio 4EX, Open Canvas 5, WACOM Cintiq 12WX User