I'ts my understanding that with the following you will have a complete communication system:
- 1 BRI (T1)
- 1 Ip/sip gateway
- 1 ocs 2007 server
- 1 exchange 2007 server running UM for voicemail and outlook voice access.
In this senrio the tradionational PBX would not be needed. The OCS 2007 is the PBX. I dont see the new sip phones yet from MS that will display the OCS client menu but I would expect them soon. In the meantime a softphone on the PC would work or calls from within the Office 2007 product family directly.