"Meanwhile, Russian officials denied the allegation. Officials of the producer of the Buk missile, Almaz-Antey, told a news conference on Tuesday that they had carried out their own analysis of traces found on the aircraft. They said even if the jet was shot down by a Buk, it was an old type that is no longer used by the Russian military.

The official also hinted that the missile was fired from a village in the Donetsk region, where Ukrainian forces were said to have been stationed at the time of the crash.

Russian deputy foreign minister Sergei Ryabkov called the report an attempt to make a biased conclusion. He argued that the report had failed to take account of the Russian investigations."

From:

http://www3.nhk.or.jp/nhkworld/english/news/20151014_06.html

So, even if the truth is out in the open (and given the tweets right after hitting the plane there wasn't much doubt) there is apparently no way Russia is going to own up to this.