The piece of the story you quote is actually self-contradicting. It calls the West Coast a bit player in coal exports, but then says Vancouver, B.C., (Roberts Bank) is the main terminal for PRB coal exports. Perhaps they meant a bit player in coal exports worldwide, not just exports for PRB coal.

I initially mentioned that paragraph purely for the perspective of exports, not for PRB coal delivery as a whole. Yes, there's far more coal being shipped elsewhere for domestic power generation than there is for export overseas.

Your "averaging just over 1 per day" figure for BNSF coal trains to Roberts Bank is apparently in reference to what's been coming through Great Falls and Whitefish. It does not take into account the two or more daily (on average) that have been coming off MRL.