just wonder: what "secrets" do u think could be at that conversations?
Perhaps warnings from another ATS unit to avoid overflying that area near Donetsk? Perhaps there were secret/unpublished internal memo's and procedures regarding the airspace in the eastern Ukraine that ATS units could be mentioning? Perhaps warnings from Rostov control? Perhaps mentioning of a Ukrainian military aircraft nearby? Perhaps critical info from the Ukrainian air force? Who knows?!
There could be lot's of extremely relevant things that could have been mentioned among ATC controllers, so releasing those ATC tapes would make a lot more sense than intercepted cellular telephone conversation between two alleged separatists wearing ski masks or a Russian officer.
There is a war going on there, and the first casualty in any war is always the truth. Additionally, with the Ukraine being an active party in this war, they have a direct and vested interest in order to perhaps brush certain 'details' under the carpet, whilst highlighting other things in order to steer towards a more favorable outcome?
p.s. when you listen to the ATC tapes from 9-11, you'll hear lot's of background info (ATC controller calling colleagues, discussing things, calling supervisors etc) that you will not be able to hear on the CVR of MH17:
https://www.youtube.com/watch?v=we9AviBVNkM