Resolution:
Assuming that new 5.2 Administrator domain is successfully created using the specified RV and Hawk network parameters, deployment of .EAR file will fail with the following error if it is under these exact conditions:

(below values are as an example: RV Daemon= tcp:7518  RV Network= ;239.1.75.18 RV Service= 7528 Hawk Daemon= tcp:7895 Hawk Network= ;239.2.78.95 Hawk Service= 7988)

com.tibco.infra.repository.OperationFailedException: Repository instance TIBCO_T-Dummy is not found
        at com.tibco.infra.repository.RepoFactory.newClient(RepoFactory.java:3258)
        at com.tibco.infra.repository.RepoFactory.newClient(RepoFactory.java:3149)
        at com.tibco.tra.tsm.plugin.TSMEngineDeploy.addRepourlProperties(TSMEngineDeploy.java:150)
        at com.tibco.tra.tsm.plugin.TSMEngineDeploy.createTra(TSMEngineDeploy.java:77)
        at com.tibco.tra.tsm.plugin.TSMBwEngineDeploy.createTra(TSMBwEngineDeploy.java:62)
        at com.tibco.tra.tsm.plugin.TSMBwEngineDeploy.beginAction(TSMBwEngineDeploy.java:38)
        at com.tibco.pof.admindomain.impl.MutableAdminDomainImpl.beginPerformAction(MutableAdminDomainImpl.java:585)
        at com.tibco.pof.admindomain.impl.MutableAdminDomainImpl.deploy(MutableAdminDomainImpl.java:486)
        at com.tibco.pof.admindomain.impl.MutableAdminDomainImpl.deployListInternal(MutableAdminDomainImpl.java:688)
        at com.tibco.pof.admindomain.impl.MutableAdminDomainImpl.deployOnClient(MutableAdminDomainImpl.java:646)
        at com.tibco.tra.tsm.TSM.deploy(TSM.java:2597)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:324)
        at COM.TIBCO.hawk.agent.maloader.MAWrapper$MAWrapperInvoker.run(Unknown Source)

This has been identified as a known defect in Administrator 5.2.0 and will be fixed in the next available Hotfix for Administrator.
Please note that issue is valid only when values for RV Network and Hawk Network have been specified.