One simple way around this, is to take one server that's on the same network as the Oracle VM Server's management network, for instance, the Oracle VM Manager system... and install something like TinyProxy on that machine. Then, use that servername as the proxy in Oracle VM Manager when you import a VM, VM Template or VM Assembly.
TinyProxy can be found in the EPEL repository (http://fedoraproject.org/wiki/EPEL). The tinyproxy RPM will install without issue on Oracle Linux. It is very easy/simple to configure and this can be a good workaround or solution to make it easy to import templates or VMs while the servers are on a more isolated network.