I have been asked several times recently about the BlackBerry® client support for OCS R2 (RIM makes a BlackBerry client that works with OCS. You can read more about it in my original post: Mobile Options for OCS).
The short answer is that OCS R2 is not supported, however there is a workaround that amounts to leaving an OCS R1 CWA (Communicator Web Access) Server for the BlackBerry client to use after upgrading to OCS R2. Trying to install an OCS R1 CWA after upgrading to R2 will not work. You must leave an OCS R1 CWA server intact before upgrading. My understanding is that OCS R2 Active Directory changes will not make it possible to install an OCS R1 CWA after the fact.
The official workaround is described in more detail here: BlackBerry Enterprise Instant Messaging is not functional with Microsoft Office Communications Server 2007 R2.
The issue is that the BlackBerry client uses the Web API used for R1 Communicator Web Access (the Asynchronous JavaScript® and XML (AJAX) API) and Microsoft no longer supports this API in the OCS R2 version of CWA. There are no current plans at this time to re-release or support this API in future releases.
(BlackBerry® is a registered trademark of Research in Motion Limited).
Inside OCS 