I thought all lines supervised. I mean, what is the reason for a line to NOT supervise? I guess I can understand test lines and loops... and maybe that's what those numbers are... test lines for the phone company to check that certain recordings are functioning properly, and all contained within the CO... but calling to other area codes I would think would take me out and back in to the system.
Remembering my early phreaking days when I opened a slick and would tap into my cousin's phone while he was on with his girlfriend. While tapped into him, I would tap into another line, dial his number, we would both hear the beep, but he was able to flash-hook and flip to the other line with just me. I could hear and witness all of this but I was "inside the system" unlike if you are at someone's house and pick up an extension, flash-hook becomes impossible.
Maybe if I could just come up with a way to create a situation where the CO would cause an "all circuits are busy" recording to play when certain numbers call my line.