I think you can use workflow for this. Sounds like you already have queues configured in CRM for each of the email addresses. So I would create a workflow with an automatic trigger on email creation. In the workflow include a check condition that tests the
bcc field. You'll need a branch for cc contain b@xxx.com and a separate branch for cc contains c@xxx.com.
To move the email to the appropriate queue add a create queue item action in each branch. In the queue item, se the queue to the correct queue and the queue item to the email (you'll need to use a dynamic value in the form assistant for this).
It might be better to have the workflow trigger off queue item creation, otherwise the above workflow would trigger for any email that is created in CRM.