What is the benefit of using a PM200 cable to connect an EIZO monitor ta a macbook?
Eizo (Netherlands) kindly and answered by e-mail. In short:
for using this monitor with a macbook, there is no advantage using the PM200-cable compared to an Apple mini-display - DVI connector.

More in detail:
(excuse me for poor english: I used google translate)


The PM200 is a cable DisplayPort cable. By using this cable you can use the EIZO CG223W-BK to give 10 bit per color (1025 tones per Red, Green or Blue). 10 Bit Color depth is as far as we know not possible on a Mac because the graphics cards do not support 10 Bit capability combined with Photoshop.
 
To make display 10 bit color depth you should use this configuration:


Use OS or Windows 7 (older Windows OS)
Use DisplayPort
Use of good quality DisplayPort cable
Graphics card must support 10 bit
Application (software) must support 10 bit
Application requires graphics card with 10 bit support
 
The application and the graphics card must therefore communicate in a certain way and we only know this possibility when using windows in combination with Photoshop CS6.

No, the PM200 cable can only be used as a signal cable (like the DVI cable). To use hard drives and printers via the monitor always be a USB cable required. To calibrate you have this USB connection is also required.
No, the monitor can not signal to another spot or third monitor. Serial looping will not go.