Can confirm this works on multiplayer.

However my friends and I ran into three issues with it in MP.

One is where none of the players' maps matched up with their actual extraction zones. Another player had the Industrial Building extraction map (extract 4) but their actual zone was the bridge. I had a downtown building marked (extract 5) as extraction but actually had to extract at the Mall Roof.

Secondly once a player triggers their extraction a number of zombies spawn in that only THAT survivor can see. We were sharing our screens and while on the bridge numerous zombies that spawned for the event were only visible to the person who had called in Extract. Some of the zombies are also invincible and only die when other event spawned zombies were killed and a number of them don't actually die but just wriggle on the ground like when they're pinned under a car. Though this did lead to our group coining the term "schizo zombies" which was a laugh.

Third and lastly, because of how successful extraction is coded, if the host is the one that extracts it kills the server.

Overall it was a fun mod, we ran it on Survivor at Insane Zombie Pop.

My only suggestion would be to also include a minimum day for extraction so players can do a challenge where for example, the chopper will show up in 30 days and then leaves in a week (max set to 37).