I could make it work by getting the best Mini displayport to Displayport cable adaptor with 4x x 2k resolution, but after making sure my graphic card has DisplayPort version 1.2.
Before I had tried a lower quality cable with no success.
I discovered Cintiq Pro requires USB-C with Alternate DisplayPort Protocol, as said in this Review on Youtube (min 1:40).
More information about USB-C Alternate protocols.
Then I found a link from the Wacom itlsef saying about HDMI compatibility: it may work in specific situations, but it has a lot of issues (not recommended).
I ran the command sudo xrandr -q and got the output:
Screen 0: minimum 8 x 8, current 1920 x 1080, maximum 32767 x 32767
HDMI-0 disconnected (normal left inverted right x axis y axis)
DP-0 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 344mm x 194mm
1920x1080 60.02*+ 47.99
DP-1 disconnected (normal left inverted right x axis y axis)
DP-2 disconnected (normal left inverted right x axis y axis)
Then the command xrandr --listproviders
Providers: number : 2
Provider 0: id: 0x1e2 cap: 0x1, Source Output crtcs: 4 outputs: 4 associated providers: 0 name:NVIDIA-0
Provider 1: id: 0x46 cap: 0x2, Sink Output crtcs: 3 outputs: 4 associated providers: 0 name:modesetting
Then the command xrandr --setprovideroutputsource 1 0 and then xrandr --current
Screen 0: minimum 8 x 8, current 1920 x 1080, maximum 32767 x 32767
HDMI-0 disconnected (normal left inverted right x axis y axis)
DP-0 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 344mm x 194mm
1920x1080 60.02*+ 47.99
DP-1 disconnected (normal left inverted right x axis y axis)
DP-2 disconnected (normal left inverted right x axis y axis)
DP-1-1 connected
2560x1440 59.95 +
1280x720 59.86
HDMI-1-1 disconnected
DP-1-2 disconnected
HDMI-1-2 disconnected
Notice DP-1-1 is now showing as connected. At this point I was able to open the display settings and see the Thunderbolt display. There I could enable it and configure. It appears to be working correctly now. I determined these steps from a post here
I then added the following command in the 'Startup Applications' dialog so that the settings persist after loging in and out.
/bin/bash -c "sleep 10&&xrandr --setprovideroutputsource 1 0 && xrandr --output DP-1-1 --auto --primary --left-of DP-0"
Best Answer
Thunderbolt displays will not receive input from Mini DisplayPort. Though the ports are physically identical, the display will only be driven by a Thunderbolt port.
The reverse, however, is possible. A Thunderbolt port will happily send input through a mini DP monitor.
For clarity:
You can read about it here (sorry about CNET) http://www.cnet.com/news/confusing-mini-displayport-with-thunderbolt/