Not sure if this has been mentioned elsewhere but Eutelsat have started broadcasting a 4k test service on Eutelsat 10A at 10E
At the moment they are using 4 x 1920x1080/50p H264 (Level 4.2 to get the block rate high enough I guess) streams (Top Left, Top Right, Bottom Left, Bottom Right)
I suspect there aren't a lot of 3840x2160 encoders and decoders (or H265 kit) out in the wild yet. (I think the 8K tests use a similar technique for both broadcast and production - they were using a LOT of slaved P2 recorders for slow-mo replays of 8K at London 2012 I believe...)
Interesting that it's 3840x2160/50p not 60p. Suspect any service launching in Europe will have to simulcast in HD and possibly even SD - so keeping the same frame rate may still be important...
Hope to try and record some of this over the weekend and see what I can do with it. I don't have a 4k display - but I do have access to >1080p resolution stuff. Think importing into After Effects (possibly converting from H264 to ProRes in FFMPEG/FFMBC?) might be a way of tiling the 4 streams into a single 4k stream?