After my post and inquiry to AT&T's PR team on Monday, I received a very detailed and refreshing informative reply.
I just learned that AT&T's CallVantage is not using SIP, and are using MGCP, but that SIP is on the edge is on their roadmap, and all of their core elements use SIP in their network.
Also, AT&T's CallVantage offers no QoS outside of their network (today) but their enterprise grade offerings have various Service Level Agreements (SLA's). As far as applications go, everything has been developed in house, no third party applications server, which is smart. No royalties, no licensing. I hear Webley has taken a similar approach. One has to realize with AT&T being the largest IP network in the world, and having peering or colocation relationships with just about all the carriers, there won't be that much hopping around.
Right now AT&T admits that until peering like relationships with the different carriers (i.e cable companies and telcos) get established, establishing QoS outside their network is difficult, but they do understand the need for it and have it within.
Being a multi-vendor carrier, there are no details on who is providing the Softswitch and they admit they are using MPLS inside their network, which more than likely means you can bet Cisco is somewhere in the network plumbing doing something to enhance the routing and traffic priority aspects of the voice traffic so the calls sound better.
The TA is coming from DLink. While it's not attractive, it should do the job. I also discovered why AT&T wants the TA ahead of the router, not behind it. To effect QoS as much as possible. When you think about it, data packets for files and emails can be reassembled, but for voice, like Streaming live, its another issue.
How this impacts streaming is a big deal and we are clearly getting to a point in time where the user needs to be able to be able to prioritze the traffic coming over the IP pipe...especially with more on demand video available like CinemaNow.
I commend AT&T for being so quick with answers and candid. Their efforts at transparency, following an era of duplicity (can you spell WorldCon or EnROB) are most welcomed by those who want substance over hype.