A single CUPS Cluster can integrate calendar information with one Exchange Cluster.  Actually, when you set it up, you have to provide the IP or hostname of the server that the CUPS cluster will connect to, but it is probably possible to use some sort of DNS-based load-sharing to allow for multiple servers within the same Exchange cluster to respond.  But if you want to connect to multiple Exchange clusters, you will need multiple CUPS clusters.

And there is no ability today to gather calendar info from the Outlook client.  One important thing to note:  The CUPC does not gather this information.  The CUPS (the server component) communictates with the Exchange server for this.  Getting the clients involved to gather calendar info would be a significant change.