Thanks so much for your assessment. So the answer to my question as to what is different with Thacker Pass is scale. The drilling decision impacted 600 square miles, and the grazing one 400 square miles. In contrast, the Thacker Pass mine will cover 9 square miles.

Presumably the BLM would have a had a difficult time realistically assessing that dozens or hundreds of drill sites would not negatively impact the Sage-grouse, and likewise would have had a hard time convincing a judge that tens of thousands of 2,000 pound cows could delicately dance around the small chicken-like birds as they ate their shade. 

However, as X pointed out, the BLM seems to have a pretty good handle on where the birds are dancing around Thacker Pass, and, although the closest one would have to be impacted, hopefully there are enough dance floors around the rest of the area that the sparse population can be happy. 

Let's face it, providing the BLM assessment is accurate, if the Sage-Grouse issue is the one that delays or sinks the mine, there's really just no hope for future US mining.