Platform Service Controller (PSC) can be deployed in different topologies, check the supported topologies here before deployment.
I have done a few deployments now using the below topology across two sites.
The following will illustrate how to check that replication between sites. Using this method provides Enhanced Linked-Mode between vCenters.
VMware KB can be found here
This example is using a Windows PSC. Open a command prompt and browse to the install directory – vmdird
First check the partners created
vdcrepadmin -f showpartners -h PSC-FQDN -u Administrator -w SSOadminpassword
Note here my second site PSC wis showing as a partner. Now run the same command the opposite direction
Now check the replication status
vdcrepadmin -f showpartnerstatus -h PSC-FQDN -u Administrator -w SSOadminpassword
You can then run this command the opposite direction. Follow the KB above if you need to create any new partners or delete any old partners.