The ERD can be found in the Application Viewer of CCB. The application viewer can be installed when you install CCB. As far as I know no separate document exists which give a total ERD of CCB, and honoustly I don't think it will be very helpfull because it will be simple way to big. You can download CCB from [Oracle Edelivery|http://edelivery.oracle.com/].
The Application Viewer is Meta Data driven, so if you want you can read the Meta Data tables from CCB and create your own full blown ERD.
As mentioned above, there is no single ER diagram for CC&B. Internally, we have developed a data model per subject area based on the application viewer for the quick reference.