This event is hosted in Trackmania and in the title(s) Trackmania² MultiEnvi. You can participate on your own and registration is not required. And there is a map pool that you can contribute to.
This event is played in »MrSloppis Multienv Titlepack. The titlepack can be found here. Players need to own all four TrackMania² games in order to play.
The Mania Exchange Knockout is an online competition where the last player to finish each map is knocked out until the winner remains.