BNSF in Pontiac Michigan

Hi, I’m fairly new to being a railfan and just started watching trains more carefully. Today I was suprise to see a BNSF Coal train in Pontiac Michigan on a CN line. Is this a normal thing? I have never seen anything about BNSF operating in Michigan.

What you saw was a “run-through”. Rather than change locomotives at Chicago, the BNSF power ran through to destination on the CN(GTW). It was operated by a CN crew. To pay BNSF, CN will either pay money to BNSF, but more likely BNSF will receive an equal number of “horsepower hours” by using CN power on BNSF trains elsewhere.