Hi David,
if I get your question right then I am afraid you cannot have virtual IPs located in different subnets (if you want to traverse the same IP between the sites, of course).
The VUs should be reachable within layer 2 switching - this is quite nicely described in this document https://service.sap.com/~sapidb/012002523100012779152014E/SAP_CCtr_INFRASTRUCTURE.pdf , check chapter 6.3 Multiple Sites. Concluded in chapter 6.3.1:
The SAP Contact Center high availability concept is based on virtual units having more than one instance sharing the same IP address and of which only one instance is active at a time. However, each instance has its own network interfaces and its own MAC addresses that must be resolvable by the router connecting to the customer.
Therefore, sites must be in the same broadcast domain and there must not be a routed connection between them.
Different story would be to have another instance of SAP CCtr in DR site, with different set of IP addresses, You must then ensure configurations replication from main DB to DR DB, remaping virtual IP addreses in Configuration database. And accept some limitations implied by different IP addresses (e.g. integration with SAP CRM).
Regards,
Dawood.