Some tests with 4K (actually UHD) in MEP2014 in response to a members question a few days ago.
I downloaded a few 4K clips H264 MP4 and Prores MOV and they import and play well - the H264 play OK even at Full preview res. but the CPU is maxed out on all cores - 95 - 100% and 50% load on the GPU to boot! - actions in the arranger are sluggish. Everything works better however by clicking the Flash symbol under the preview window to reduce the preview resolution and I can add a page peel transition and Title which play smoothly with the CPU having some headroom at 60%.
Export seems restricted to H264 in MP4 or MOV although this would probably be possible with other codecs like Prores, if they were on your system. There seem to be no export presets in the system ( not to mention anything about 4K or UHD workflow in Help) but the correct resolution template comes up when you try to export. An appropriate bitrate can be entered in the advanced encoder settings.
The Prores MOV did not play well at full res probably because MEP is optimised for playback of H264 by invoking the GPU to help decoding.
Not an all encompassing test and results will vary according to you system and footage but reasonably impressive. Creation of proxies should further improve the handling also but I have not tried that.