If you are concerned about the challenges with fax over G.711, you may be interested in a webinar which focuses on such topics and also focuses on how SIP and T.38 can improve the reliability of fax over IP.
This particular webinar is fifth in a series consisting of the following webinars which are archived for your viewing pleasure:
"Break Free" – Leveraging SIP in Developing Enhanced Applications
Building Applications with SIP – the IP Contact Center
Building Applications with SIP – Conferencing/Collaboration Solutions
Call Recording – Evolving from TDM to VoIP by Transitioning Challenges into Opportunities!