Disclaimer: I do not work for AT&T (right now) and do not use their A-List service.
Reading this page:
http://www.wireless.att.com/cell-phone- ... a-list.jspI found this (emphasis mine):
"Calls
to and
from your A-List numbers are not charged against your rate
plan, Mobile to Mobile, or Rollover® minutes."
That leads me to believe that you could add your Google Voice number to your A-List (not the number Google calls from when using their app, but the one that calls you when dialing with VoiceCentral) and you would not be charged for calls placed using Google Voice via VoiceCentral.
Can any users confirm this?