CA EFS certificate on encrypted SMB share folder issue

Hi, I have an issue I don't understand.
In my lab I have 1 DC 2008R2, 1 Member Server 2008R2 with Enterprise CA, 1 win7 Client.
I have created 1 duplicate EFS template and 1 duplicate EFS Agent template.
The User account on client received the EFS certificate correctly from CA.
If I encrypt a folder on  the client locally, all works well: I see that the the thumbprint of the certificate used for EFS encryption, match the thumbprint of the certificate issued by CA.
When the same User on the client encrypt a file on a shared folder on DC1, the thumbprint doesn't match the thumbprint of the EFS certificate obtained before from the CA.
It seems that the certificate used on the SMB share was self-signed!(not issued by CA)
Can someone explain this behavior? 
I have no trace of this selfsigned certificate on Certificate MMC.

Thanks!
Andrea