So I got my GS 502 and hooked it to the Uverse gateway....works fine. As expected, a softphone on the same net rings, but answering call leads to a connection where the caller hears me, I hear nothing. Makes no difference whether I port forward udp ports to the GS or not. I gather this is really
an expected behavior.

Tech support said to "port forward the GS and put the SIP or softphone in router's "DMZ+"....but I think this would be afail as the way the 2wire RG works, DMZ device gets all ports, all traffic not specifically assigned to other ips........so UDP ports can still only go to one destination ip. What I'm investigating now is placing byod devices on another net in the home courtesy of additional public ips that I may assign to them....multiple DMZs kinda.
Trouble is, while I see ATT users saying this can be done and is available, their CS reps don't seem to know what I'm talking about.