https://www.polygon.com/2017/9/18/16329656/fortnite-cross-platform-play

There was briefly cross platform play in Fortnite between users on Xbox One and PlayStation 4, over the weekend, Epic Games confirmed today.

Gamers in the Fortnite subreddit spotted what they thought was cross-console play in the co-op sandbox survival game over the weekend. While others were skeptical that Xbox One users and PlayStation 4 users were in fact playing together (thinking someone had mistaken a PC gamertag for an Xbox Live handle) an Epic representative said this afternoon that’s exactly what was happening.