Just wondered if two cisco router with a classic VPN tunnel would work for remote phones on the UC320. I have heard that because of the UC320's provisioning of the handsets their needs to be a way of turning off things like the wifi settings or an SPA525g2 will try to connect to a local SSID when the handset is remote.
The UC320W doesn't support remote phones and I'm afraid one can not simply set up a VPN and expect them to work remotely. Part of this is due to some internal messaging using IP multicast. If the customer requires remote phones, then the UC500 series is a better feature fit.