Hi,
When you install the SEP 12 SBE, it make a check for presense of communication settings at the follwing location:
C:\Program Files\Symantec\Symantec Protection Center\Server Private Key Backup
So, if you create a similar folder structure on the new server. And copy all the contents of the folder from previous spc in that new folder, at the time of installation, installer will detect presense of communication settings and ask you if you want to use those settings to re-establish communication with those clients.
Please let me know if this works for you.
Best,
Aniket