Paul:
After the end of the busy tones here you get :
either clunk, click and just dead silence if you've any line powered feature phones connected their displays will go blank. Or else a kinda weird fading of the busy tone and the a click to complete silence and the power is removed (again feature phones and memory phones loose power)
It has one very handy effect. If I leave my Siemens DECT phone off hook accidently once the power to the line is cut it automatically hangs up!
If the power is completely cut however i have no idea how it detects when the phone is back on hook though. I presume it must keep some kind of very low power DC on the line regardless.
