Avaya 4.0 is now Certified for SIP direct.

Avaya 4.0 is now Certified for SIP direct.

You could use direct SIP connection for a POC and then rip and replace :)

Get more information here

IP-PBX Vendor
Tested Product
Supported Configuration
Software Versions Tested
2007 R2
2007

Avaya
Communications Manager SIP Enablement Services
Direct SIP
4.0

Known Limitations:

• Configuration requires setting "Alternate Route Timer(sec)" value from default of 10 sec to 30 sec. The configuration should show "Alternate Route Timer(sec): 30" in the corresponding SIP signaling group.
• When an call is ringing to the Office Communicator user, the caller (either on an Avaya station or a PSTN line routed through the PBX) will not get ring back tone. This issue has been resolved by Avaya with the 5.x software releases.
• Quality of Experience reports will not contain information regarding jitter and packet loss.
• Comfort noise generation is not supported. As a result, comfort noise is not played on Office Communicator.
• ISDN Failover is not supported from an OCS perspective. If the Avaya PBX is being used for PSTN connectivity and multiple T1's are being utilized, an OC client will not retry a call based on a T1 being unavailable. It may be possible to configure the Avaya to not assign outbound calls from OCS to an unavailable T1, but this configuration was not tested.