A Grand Truck/CN worker befriended me after I called him over to ask some questions. Not sure what he does, I will ask, but he seems to work with the driver to add more freight cars. He's never seen someone painting but see cans all the time.
His co-worker writes and takes pics on the job. Some of the workers are very into the graffiti, others hate it with a passion, and some don't notice it at all. He did say hew knew several co-workers that write but didn't know what names.