Acer UHD4K2K not working through Thunderbolt
Got the same setup, and all is working fine here - but some things you will need to take into account:


My ACER didnt ship with an HDMI cable, it came with a Display Port Cable, as i am having the XB280HK Version - and thats the only way that makes sense (technical restrictions on other connection methods, as you stated above) to connect it.
A Thundebolt cable is NOT a Thunderbolt-to-MiniDP cable! Thunderbolt has an integrated Handshaking, and is for Data-Io only - non Apple Products, like the Acer cant make sense of the Thunderbolt Data and wont be able to recognize it as "Display Data"
SOLUTION: Make your life easy and get a third party Mini-DP cable. The thunderbolt PORT will recognize what you want from it and switch mode to be just a mini-dp port. Dont know where you are, but here is one on Amazon USA: http://www.amazon.com/Cable-Matters-Gold-Plated-DisplayPort-White/dp/B004CAGDSW/ref=sr_1_2?s=electronics&amp;ie=UTF8&amp;qid=1416467966&amp;sr=1-2&amp;keywords=mini-dp+cable


Lastly be advised, Not only HDMI has a restriction with the 30 HZ, but also any model of the MacBookPro prior to the IRISPRO Graphic Chipset (introduced late 2013) will not give you more than 30Hz on that resolution... (discrete Graphics aside obviously)



Greetings from Ibiza