The only workaround that I've come up with is to suppress the click domain on the machine that is opening the CC/BCC email addresses. This can either be implemented by a local firewall rule, or editing the hosts file on the machine.
For example, add the following entry to the hosts file on the machine that is opening the emails:
0.0.0.0 click.subdomain.mydomain.com Where subdomain.mydomain.com is the SAP domain of the Marketing Cloud account. This will block the click domain (used to track email opens) so itemails will not be recorded as an open.