Indeed, that was my pointExcept Coldharbour is faction gated. But yep, it's in line with the concept of our Coldharbour zone.This is EXACTLY Coldharbour. No factions involved, just random adventurers wanting to work together.The factions working together? No.
Random adventurers who happen to be members of the Fighters and Mages guild, who elect to personally work with adventurers who hail from other parts of Tamriel working together? Sure.
Yes? That's exactly what makes it cross-faction. As Vizier said, a situation where the Fighters and Mages Guilds pull members from all over Tamriel to fight the Deadric threat with the consent of the alliance leaders. They've pulled members (and independent adventurers, like the Vanos siblings and Lady Laurent) from all over Tamriel; hence, cross-faction.