West Haven, CT
Uverse doesn't care if it is voice or fax because everything is digital between the RG, through the VRAD and into the system. On an incoming call, the RG provides the ring signal and converts the digital signal to a voice signal. Normal calls and fax calls are all "voice grade" and it is the set that distinguishes the difference. A fax modem (the set) will answer the tones sent by the other fax machine then sync up and receive or transmit the information.
Simply put, Uverse handles voice calls, fax and dial up modems with no problem. I've been using Uverse VoIP with a fax and an occasional dial up modem (for work) for almost three years with no problems at all.