While it is a fact that some practitioners in Tibet eat meat, it does not mean that all Tibetan practitioners do or that the scriptures condone this behavior. One cannot find anywhere in either the Mahayana sutras or the Vajrayana tantras that deem meat eating acceptable.
One thing does worry me though. Some practitioners from China who used to be vegetarian went to Tibet to study Vajrayana. Instead of learning the essence of Tibetan Buddhism, they adopted the bad habit of consuming meat, even to the point of being excessive sometimes. They believe this is the way of real Vajrayana, and that as a yogi of Vajrayana, eating meat is only right and natural.

[Excerpt from Luminous Wisdom Book Series 1: The Right View ~Why Vegetarian?]