I actually run 7962g + FreePBX too, using sccp_manager and phone-integrated SSL-VPN. It took more hair pulling and shady patching than the SIP route, but now I

I actually run 7962g + FreePBX too, using sccp_manager and phone-integrated SSL-VPN. It took more hair pulling and shady patching than the SIP route, but now I can make intercom calls over the Internet! That way I don't need a direct L1/L2 link between "offices". Solves NAT problems too, because it's all in-band signaling and media transport over single TCP connection.