[mssms] Implement SCCM 2012 encryption with 3rd party CA?

[John]

Hi All,
We are looking to set up a PKI to enable encryption in the SCCM 2012 
environment, but unfortunately, we do not have a local CA.  We use a 3rd 
party (GlobalSign) for our certificates, however, I'm not convinced they 
can provide the client certificates.  Has anyone else managed to get 
this working with an external CA?  I really need to know if this won't 
work and we're just chasing our tails. Essentially, my concern is this:  
When we set up a local CA to issue certificates, we do it by creating a 
template and allowing the clients to auto-enroll for the certificate, if 
we have a 3rd party CA, how does that mechanism work, if at all?

Thanks in advance

John