asterisk users - Jul 2004 - Can Asterisk register through a sip proxy with a username incorporating a different server?

For those that read my messages about broadvoice this will be completely 
redundant, but I am looking for a larger audience (and know most people 
must pick and choose which messages they read).

To explain the reasoning behind this question to every reader, 
broadvoice had a failure yesterday, but I plugged in my broadvoice 
configured Cisco 7960 and it STILL WORKED.  They apareently are built 
with a considerable amount of redundancy, but Asterisk seems to be 
unable to utilize it.  I will admit it is possible I have missed 
something with the configuration, but I have searched the wiki and 
mailing list.

The cisco 7960 phone is registering itself as 
<phonenumber>@sip.broadvoice.com via proxy.broadvoice.com.  It looks up 
the SRV record for proxy.broadvoice.com and uses 
proxy.lax.broadvoice.com and proxy.dca.broadvoice.com.  It keeps itself 
registered through both proxies.  This was verified with ethereal.

The Cisco phone is configured with sip.broadvoice.com as the sip server 
for the line.  proxy.broadvoice.com is listed as the outgoing proxy in 
the configuration.

What would it take to get Asterisk to do the same? 

Thank you,
Charlie Hedlin