I had to go back and look at that diagram again to make sure before i posted.
To answer your questions:
Because the power cord has three wires in it:
The 20.0 main output of the P2140 goes only to the main power of the laptop.
The ID line that comes from the brick goes to the laptop.
The ground from the P2140 is connected to both the brick ground, and the laptop ground.
The white and green wires are not the ones on the plug itself but the relay pins on the inside of the P2140 that come off of the board itself. these are connected to the power button on the dock, or the power button on the laptop. (The P2140 just connects them together to pulse the laptop on or off)
Yes I was able to get BOTH a successful startup and shutdown from the P2140. I am NOT using the USB at all. I remember having to flash the P2140 to the newest firmware and had to adjust the settings so it would have a shorter start pulse. because when it did the startup with default settings the system on pulse was too long and would turn on the laptop and then it would promptly turn off (2 secs). If you have any other questions let me know.
I actually do not use the M1710 laptop anymore because it is incompatible with the touch screen i wanted to use, but besides that it was a great working system.
Post here or PM me if you need any help.