Activated immediately after the start of Chapter 2, the players can choose to activate four of the five power generators around the city and restore power. Doing so will open up the gates around Apollo. There are several reasons to do this.
Proceeding through the Scrapyard is the fastest way getting in. Banelings will not spawn until two minutes after the Dome is destroyed from inside on Recruit mode.
Proceeding through mission on Hardened mode banelings will spawn in several different locations but are not random. It is possible to stand and wait for banelings to spawn at a safe distance to avoid getting hit and gaining exp for your character(s).
Other reasons are less significant, the team wishes to avoid the baneling trap in the Scrapyard entrance or has selected a location to hold out for the Black Ops or Queen that will be too long a trip without the doors open. This mission gives no rewards other than increased access to the city.