Outposts set up by the Highwaymen can be scavenged for Ethanol, a valuable resource needed to upgrade homebase Facilities.
They will be marked with a pink banner on your map when you get close to them - scavenged Outposts will be marked in your General Progression (zoom out fully on your Map to see it). You do not have to Scavenge an Outpost once you capture it.
The Highwaymen will look to take back over the location at the earliest opportunity and once they do, they will improve their defenses with the help of - you guessed it - more Ethanol.
This will make the next scavenging attempt more challenging!
Scavenging the same Outpost multiple times will not boost your overall progression, but the loot will definitely make the Prosperity community happy. The loot received gives you the chance to earn certain cosmetics!
Let us know if you have any other questions!