Does the Apple Cinema Display 27" power usb via plug or bus?

[Zellio]

Since I have usb 3.0 ports I could power up to 900 ma vs the 500 ma that usb 2.0 does. But if the usb slots are all powered by the wall adaptor, then that is 1500 mA vs 900.

This is probably a dumb question, but I want to know for sure.

 

[JassonT]

Does the Apple Cinema Display 27" power usb via plug or bus?

I use two thunderbolt displays with my MacBook Pro. I have a dock plugged into one of the displays for charging and syncing my iPhone 5s and when my MacBook is not plugged into the lightning displays my phone still charges. This is how I know on the lightning displays the USB's get there power from the monitor being plugged into the wall not the MacBook.