For these AUs (this isn’t at all an ability in canon Supernatural), all archangels share the same awareness of other timelines, some stronger than others. 

Gabriel is one of the ones that has a sharp awareness of other timelines, because he likes to dabble in alternate realities on the side (The Lounge in BA, Changing Channels and Mystery Spot on Supernatural).

He will show up in other, future stories. He better just watch out if anyone recognizes the bartender in the Lounge!