Later, another Xbox One Gamertag with spaces in it was spotted in an online match on PS4.
Oops, it looks like for a brief few hours PS4 and Xbox One cross-play was available in Fortnite. PS4 players noticed it because Sony doesn't allow gamers to use spaces in their PSN usernames, while Microsoft does for Xbox Live gamertags. Epic Games has their own game launcher (because who doesn't now a days?), so for this user name to appear on Xbox Live and have footage of the game is a pretty definitive answer.
Does this mean we're finally getting cross-platform play between the two long-standing rivals?More news: Auckland flights cancelled over fuel shortage
While Sony has revealed that the company would not support cross-play for certain titles even with Microsoft backing, it is unknown at the time of writing whether or not the feature has been approved secretly, or if the instance just happened to be a glitch. The problem is, even for games like Minecraft and Rocket League that offer cross-play between PC, Xbox One, Nintendo systems, and mobile phones, Sony nearly never wants to play along.
In a recent interview with Eurogamer, Sony head of global sales and marketing Jim Ryan described Sony's stance against cross-console play as "a commercial discussion between ourselves and our stakeholders" and "not a profound philosophical stance".
And yet developers have said that switching on PS4-Xbox One cross-play would be relatively simple. Of course, it's always been technically possible for Fortnite and many other games, all waiting on Sony's approval for them to actually enable the feature.