Note. To the best of my knowledge this is not based on any existing Fallout Equestria storyline, nor does it follow any particular plot in Fallout 4. This is just the narrative that popped into my head as I worked on this piece. This is a patron reward for Skyline Twilight
 
Starlight Glimmer listened through her headset to the steady stream of radio traffic on the Underground Railroad’s communication network. Adjusting the sling on the submachine gun slung around her neck the light mauve unicorn leaned forward and looked at the old, pre-war Public Works map. It showed the vast network of sewer lines that once serviced the needs of the city. She rested both of her hands on the table and stared at it intently for a several minutes. Extending an index finger she started to trace a few of the more major lines. Finally she looked over at her two guests.
 
“Amber. Sweetie Belle . Thank you for providing this document. Please convey our gratitude to the Overmare of Stable 69 for providing this. This map is very extensive, and it will help the Railroad a lot.”
 
Starlight sighed. “However the Institute has made a much more comprehensive survey of the old city infrastructure. This is how they’ve been able to gain access to the inner parts of the city.” She removed the pencil from behind her ear and tapped the map several times.
 
“It was how my team was able to move several recovered power turbines down into our facilities.” She stopped for a second. “Well, I mean when I was part of them.”
 
The mare paused and gave her undivided attention again to the radio traffic. Then she looked back at the pony-dragon hybrid stallion and unicorn mare who patiently stood nearby. “Our most recent recon patrols have observed increased Institute traffic through the old sewer system. This along with my surviving network of contacts in the Institute seems to confirm my suspicions that Chief Researcher Twilight Sparkle is making another attempt to reconstruct one of the fallen Royal Sisters >>2193714.”  
Starlight’s deep violet and green mane swayed from side to side as she shook her head again. “Unfortunately Twilight and her staff haven’t learned the right lessons from their last failed attempt. In their quest to recreate the Princess of the Moon they instead unleashed another torment upon the world.”
 
Amber started to say something when suddenly the Commander of the Railroad tensed up as some bit of radio traffic caught her attention. Reaching up she toggled the microphone on her headset. “Trixie! Please repeat your last communication. Over.”
 
Starlight turned her back and immediately stepped away from her two visitors. She wandered over to the far corner of the old hotel ballroom that was acting as the Railroad’s current command center. For the next couple of minutes she had a very animated conversation with somepony on the other end of the line. Neither Amber or Sweetie could make out she was saying, but it was obvious that something was happening. Off in the far distance they could hear the sounds of a firefight. This went on for a minute of so before subsiding.
 
Finally Starlight came wandering back. There was a scowl etched across her face. “ Sorry. That was an example of increased Institute traffic I was talking about. Now where were we?”