Installing new SCCM 2012 infrastructure over an existing SCCM 2012 Infrastructure

Question

Greetings,
I currently have a standalone SCCM 2012 environment running in production.  This implementation isn't in a hierarchy and doesn't support Macs (non-PKI/HTTPS infrastructure), but is managing 1500 PC clients beautifully.
However, we have some sites out-of-state that need to be in their own Primary Site, as well as Macs across both sites need managing as well.  
I have made a new environment entirely on 2012 infrastructure (2012 SCCM, 2012 Server, and 2012 SQL).  This includes a CAS at the top, a PRI for my current site, and SQL for both (all on different hardware, new names, etc.).  I've installed a PKI
infrastructure, and it's currently working fine managing the three servers it contains.
I need to start migrating all of the clients and services to the 'new' SCCM implementation, but pushing the SCCM client installs to over the old SCCM doesn't seem to change any settings.  Nor does changing site settings in the control panel of a client.
Anyone know how to configure new site settings without re-installing the SCCM clients on the 'old' infrastructure?
Thanks~

Answer 1

Have you ever used group policy for site assignment? This caught me out when upgrading to a new site code. If it has ever been used, it brands the registry and no amount of tinkering in the configuration manager console or client installation methods could
fix it.
To fix our site, I removed the offending GPO settings and set the 'GPRequestedSiteAssignmentCode', 'GPSiteAssignmentRetryDuration(Hours)' and 'GPSiteAssignmentRetryInterval(Min)' items under 'HKLM\Software\Microsoft\SMS\Mobile Client' to delete via GPP.
Details and symptoms I found at http://blog.coretech.dk/heh/new-agents-will-not-re-assign-to-configmgr-2012-site/.
Jilhad,
Looks like most of the machines I was testing were indeed installed via GP before I was able to install via the console.  
Deleting those registry keys allowed me to push the install over the old environment using 'Install Client' from the 'Devices' console, specifying to re-install client.
Now, I just have to figure out a script to remove those keys via SCCM
***Most of you were wondering why I was installing a CAS environment, it's really because this site doesn't conform all that well to our policies, and they will ultimately be administering their own environment.  It seemed to me that it would be easier
for me to delegate control/permissions/data using a hierarchy.  It was a tough decision, ***
Thank you all for your help!