I am not sure but ANIRA is just internet and connectivity is through IPsec? I have worked at AT&T and we used to configure this ANIRA Service but it was a couple of years back and have pretty much forgotten about it....
Check the latency (150ms one way), Packet loss (less than 1%) etc. normally that should be fine, Also make sure you have sufficient bandwidth. the only problem with IPsec over internet is going to be QoS. Check with your AT&T engineer if the QoS markings are honored and you can mark the traffic.
-Terry