Re: Two Different Sites vCenter and Single SSO in only one site

Yes, you can have a single SSO and multiple vCenter Servers pointing to it.

http://pubs.vmware.com/vsphere-51/index.jsp?topic=%2Fcom.vmware.vsphere.security.doc%2FGUID-B472DA47-94DB-40EB-9F0C-48743FADB4A9.html

"Deploying vCenter Single Sign-On in Basic mode means that a standalone version of vCenter Single Sign-On is installed on a system. Multiple vCenter Server, Inventory Service, and vSphere Web Client instances can point to this standalone version of vCenter Single Sign-On."