RK you are spot on
I know somewhat about the cabotage issue because I was once detained (nearly arrested) at the Lacolle QC. / Champlain NY. Crossing several years ago.
I was working as a dispatcher for Maisliner at the time. We were hauling lots of textile into NYC. Quite often the textiles were quota goods, requiring serious verification by US customs. We would hand in a bunch of documentation written in Chinese on rice paper, I still have no idea what they did with that stuff.
What this meant was that the driver could spend from 2 to 8 hours trying to clear the shipment.
We were busy as hell and had a shortage of drivers. Therefore we decided to be a RESPONSIBLE and SAFE carrier. We had asked our inbound driver to shut down on the US side at the truckstop and we would switch loads with him once the switch driver had cleared the quota goods at US customs.
We must have been short a local driver because I took a truck myself and went to do the switch.
I went to the booth and spoke to customs, the officer noticed I was a little overdressed, and asked me where I was going. I gave him the details and he had no problem, I was sent to inspection which was the norm for quota goods.
Although there was a DOT officer in the booth at the same time and he had an issue. The two guys argued amongst themselves and finally I was sent inside to immigartion.
I was now fully detained, wallet , cell phone and anything on me confiscated. I narowly escaped a full cavity search!!!
I was questionned by numerous officials moving higher through the echelons. The only thing that had saved me was that I had in my wallet a student ID card for McGill university, I was taking some night classes in law. It was touch and go for the last two hours, Immigration was deciding if they were going to seize the tractor , trailer and goods.
These guys were serious, nobody could get a hold of me for that period of time. I would not recommend this for the faint of hart.