I made a short video today that includes this new Call Director in a rotary dialing test for the new rev of my "one board KSU"; one of the new features being to support rotary dialing on the intercom line, as previous versions only supported touch-tone.

Of interest, I was able to use the amber "Flash" button on the Call Director to simulate rotary dialing the three different extensions (around 0:30 or so in the video).
I couldn't use the switch hook to do this because that also cuts out the A lead, which kills the intercom circuit completely, preventing rotary detection.

Video: 1A2 KSU Test of Rotary + DTMF Intercom Dialing
[Linked Image from seriss.com]

For anyone wondering, pressing the "clear" button (to the right of the amber button) simply "hangs up" by popping all the line buttons up.
So I guess that is how someone with a headset would hang up. And I guess when the phone rings, pushing a line button would immediately connect the headset to the call.