At the Ontario/Quebec provincial line, as Bouchard is walking away and Ward is speaking to him from behind, Ward's position changes between camera shots, although he's depicted as standing still.
At the end of the scene "meeting" David Bouchard, his wife tells him something is happening at "quatre heures", which the English version's subtitles translates as 4:00. However, Quebec French uses a 24 hour clock, she should have said "seize heures" for 16:00 or 4:00pm. So she said this event was at 4:00am.
Although they don't specify what highway the crime is on, there are only two highways of that size entering Ontario from Montreal. Both have a significant No Man's Land between the Welcome To Ontario sign and the Welcome To Quebec sign. Such a crime scene on the Ontario sign would be clearly in the Ontario jurisdiction.
The "Welcome to..." sign at a border is never right on the borderline. Each state/province/country has its own sign, a few meters/yards inside its own territory. A dead human body, half in each jurisdiction, would be on the ground, not draped over a sign.