Russia took down another Malaysian Airlines plane and virtually nothing has come of that.
And I don't think they accidentally shot down the plane. They might've assumed it was a different plane, but from what I could tell, they intended to shoot it down. If I'm trying to avoid accidentally shooting down planes, I'm generally not firing surface-to-air missiles about the place.
It was an arms-length Russian crew then, and that could well have been the case with the other Malaysian plane. Professional support but professional deniability.