Its an addition to Cassidy's ending, by completing Heartache by the Number by exposing the Van Graffs and the Crimson Caravan to the NCR Authorities.
I didn't get it the first time through the game but I did on my second.[in both play throughs I completed the quest the non-violent way]

Well after the first part about the NCR using the evidence to blackmail the crimson caravans and the Van Graffs, which I saw both times.

It mentions that Gloria and Alice were removed from there positions out east, but were killed on the way back west when there caravan was attacked by raiders armed with high tech weapons, no cargo was taken. The gun runners denied any involvement saying they had no... public motivation for the attack. I do think that stealing there manufacturing plans for Alice does have consequences.

As the only other MAJOR difference was NCR took the dam instead of Yes Man.[I doubt the khans, enclave or the brotherhood involvement had any effect there]