Since the announcement of Fortnite Battle Royale on mobile, there has been a lot of confusion as to how cross play will work between all of the different platforms. This has only been worsened by today’s announcement of Xbox One support so here’s a quick explanation which should (hopefully) clear everything up.
Mobile and Console players are not forced to play against PC players, it is entirely optional and achieved by partying up with a PC player in the lobby menu. If a Mobile player queues up with a Console player, they will be put into a Console game. If a Console player queues up with a PC player, they will be put into a PC game.
Note: PS4 and Xbox One players cannot play together, as clarified on reddit:
Can only play in PC/Mac lobbies, no matter who they queue up with.
Can play in PC/Mac and PS4 lobbies.
Xbox One Players
Can play in PC/Mac and Xbox One lobbies.
Can play in PC/Mac, PS4, Xbox One and Mobile lobbies.