I have hooked a Asus PB278Q to my current latest (mid-2014) rMBP using a 1.2 miniDP to DP cable and it seems to be working fine. I've calibrated it per http://www.tftcentral.co.uk/reviews/content/asus_pb278q.htm#calibration.
But in the hardware Graphics/Displays section it shows
Television: Yes
Shouldn't it say RGB?
But in the hardware Graphics/Displays section it shows
Television: Yes

Shouldn't it say RGB?