The location of the virtual machine is provided by DeployDestination, which will be passed in NetworkGuru#reserve and NetworkElement#prepare.
During the virtual machine migration, it actually changes DeployDestination and it looks like that it will tell that event to network components as it has NetworkManager#prepareNicForMigration. The problem is that althogh the interface has that method, NetworkManagerImpl does not tell the DeployDestination changes to network components.
So IMHO, we need to add calls of NetworkGuru#reserve and NetworkElement#prepare in NetworkManagerImpl#prepareNicForMigration . And then, we also need to add calls NetworkGuru#release and NetworkElement#release after the migration, otherwise the network resources that plugin reserved will be kept even when the vm leaves off.