I figured this out, with the help of some bright guys on DSLreports voip tech chat forum http://www.dslreports.com/forum/r267429 ... art=40#end
It seems Verizon has implemented a SIP proxy, but it only performs it's mangling on port 5060. Switching to port 5061 allows VoIP over 3/4G to continue unmolested. And with 4G bandwidth, the horror of cellphone audio can easily be supplanted with G722 or G711. So in the end, it is the fault of Verizon Wireless. Doesn't everybody know by now that SIP ALG or other such manipulative tomfoolery by the router is not helpful? We have SIP clients and servers that have long been designed to traverse NAT without the "help" of the router.
If there is anything that can be done to make Bria more resilient, I suggest it is still worthwhile. See the last two pairs of logs posted in the above thread failed using port 5060 and successful using port 5061.