This is probably a Canadian National unit, although still in the BC Rail colors. CN power often shows up on BNSF trains in the Pacific Northwest; I've also seen former Wisconsin Central and Algoma Central units in their "fallen flag" schemes, along with the standard CN black, red and white.

Every so often, other foreign power passes through on both BNSF and UP. You're likely to see NS and CSX units, even some in still in Conrail blue; Montana Rail Link power shows up on BNSF, as well as Kansas City Southern. You may even see KCS of Mexico and Ferromex. UP trains coming down from the Eastport, Idaho border gateway with Canadian Pacific will have CP and CIT Group (CEFX) power along with UP's own locomotives.