I have 1 HA pair at primary site and another HA pair and DR site.  My policy manager is located at DR site.  Subnets of your devices does not matter as long as devices can talk to gateways and gateways can talk to EMC ESRS servers.
We have 2 Sites (Primary & DR). We currently have XtremIO, VNX, Isilon Cluster and a Data Domains Cluster. It's broken down as follows.  Primary Site XtremIO, VNX, Isilon Cluster and Data Domains Cluster  DR Site Isilon and Data Domains Cluster  Does EMC recommend (1) ESRS server in the Primary site and 1 ESRS server in the DR running in a HA pair and (1) ESRS Policy Manger. Anything else that we need to know.  Also the units are on 3 different subnets, examples below. Will that matter? XtremIO is on subnet (192.168.2.X) VNX is one subnet, (192.168.3.X) Isilon & Data Domains is on the same subnet (192.168.4.X)
ESRS 2 Site Deployment Recommendations and Questions