The new Team Up, is not three separate stages like the old Team Up. Instead it is three of previously played stages from Story or Combat Tests. These three stages will be at a higher difficulty and the three stages will vary from day to day.
The reward will be a good amount of Bropoints, and also for the final stage, 20 crystals.
Here are three example of Team Up missions.
Team Up 1 Arcadia, Dodgy, Squire
Team Up 2 Blaster, Dodgy, Legatus
Team Up 3 Arcadia, Dodgy, Legatus