What leads you to believe that it is nighttime when this video was taken? IR looks like IR, day or nighttime.
That's not exactly true. It depends on the wavelength of IR light that is employed by the FLIR, and how the surfaces are heated by direct sunlight.
On a sunny day, you would expect to see shadows because they are colder, and objects like the truck would be much warmer on the sunlit side. In this video, the trucks don't have shadows, and the heat signature of the pickup truck engine predominates over the solar heating (if any).
The lack of shadows and differential solar heating, indicate that this video was either shot at night, or on a cloudy day with no direct sunlight.