The lookout don't let you lower the bridge. He can't have war in two fronts.
The other being fewlocks (behind the bridge) and the other wombats attacking their bins.
Maybe you could make him believe the fewlocks are attacking.
While the siren is wailing it is your change to cause wombat attack!
NOTE! There is a known bug with the timer. It should not run out in seconds!
The wombats are attacking their bins.
There is the battery powered platypus in the farm house. Maybe it would go for wombat.
Kick the siren in the future zone, walk into the Elysium cluster and put the battery powered platypus into the bin before the timer runs out.
Now he is more concerned about wombats. You can pull the lever to lower the bridge.