The transition itself is a simple dissolve between two matching shots taken at different times of day. Throughout the piece this matching-shot technique was used, although sometimes they opted for a variable luma key to make the transition look, I don't know, "cooler." Most likely the camera was mounted on a motorized slider to closely (though not perfectly) duplicate the motion.
I think ann is right. static shots at high res ( 4k etc.) put into 1080 or 720, so lots of room to do slow pans, etc. in post ). the static shots are small moves compared to walking through space with steadicam (self leveling camera mount ) ...all the transitions from light to night are really small moves in post ( IMO ) using static camera shots.