From what I can make out there's no way to have a line key on a phone to monitor/seize a SIP trunk, or am I missing something? We would like to set up all the phones to have access to 4 shared FXO lines, and then several "shared SIP" lines in the same way. The only way I can see of doing this is to use a steering digit to route through the SIP lines but then there is no way to monitor these lines?