Microsoft finally released the Web Service Provider for OCS 2007 R2 & Exchange 2010 Outlook Web App:)
With Microsoft Office Communications Server 2007 R2 Web Service Provider, administrators can implement basic instant messaging and presence functionality for Microsoft Office Outlook®-Live users. Prior to the Web Service Provider release, Outlook-Live users accessed this functionality through client applications such as Microsoft Office Communicator 2007 or Microsoft Office Communicator Web Access (2007 release).
Web Service Provider does not introduce features excluded from Communicator Web Access (2007 R2 release). It simply gives Outlook-Live users an alternative method for accessing basic instant messaging and presence information. For example, senders of an e-mail will now be able to view presence information from within the Outlook-Live application.
With Web Service Provider, Outlook-Live users cannot manage access control lists (ACLs), perform a contact search or expand a distribution group, perform desktop sharing, or incorporate audio as they can in the Communicator Web Access (2007 R2 release) or Office Communicator client applications. The functionality exposed by Web Service Provider is a subset of the functionality available through Communicator Web Access (2007 release) and should not be considered a Communicator Web Access (2007 R2 release) replacement.
In the Web Service Provider operating environment, Outlook-Live is the client application. Web Service Provider resides on the same server as the Outlook-Live server or Microsoft Exchange 2010 Client Access server and bridges the gap between Office Communications Server and the Outlook-Live client. To facilitate this process, a trust relationship must be established between the server running Office Communications Server and the Outlook-Live middle tier server.