The clip started out of course with Tracer hiding in the bushes right next to a choke point. The player moved the camera around a little bit to show that Tracer is basically invisible from all angles. The match started and the team escorting the payload headed out of the spawn point. They managed to push Tracer's team away from the payload, but lo and behold, even though they have a teammate sticking with it the whole time, it's still contested. Roadhog and Ashe run around trying to figure out where the enemy player is.
Reinhardt got out and tried to push but that didn't work either. Tracer's team finally came back while Zarya clipped Tracer trying to get at Lucio. Tracer realized they were made and scrambled out of the bushes before Reinhardt can punish them with a hammer to the face.
It's absolutely amazing how long the Tracer was able to contest the payload, wasting precious time for the enemy team. Goes to show, always check the bushes.