Microsoft has released one more KB article 2806021 to fix the ConfigMgr 2012 SP1 client registration issue/s with Mac OS workstations. It seems this is applicable for https communications with PKI certificates.
When you try to register a Mac client in System Center 2012 Configuration Manager Service Pack 1 (SP1), the registration process fails. When you check the MP_RegistrationManager log in this situation, you see the following error: The certificate chain processed correctly but terminated in a root certificate not trusted per ConfigMgr CTL.
More details about this issue here.