Back in 2019 a YouTube channel by the name of "Prototype Preservation" disappeared just as quick as it appeared. This channel focused on early pre-alpha versions of Call of Duty Black Ops 2, mainly focusing on the multiplayer content showing the many ways that the game has progressed during its early development, also showing many features that were cut along the way. It is theorized that many of the dev kits they utilized were sourced from "Prototype Warehouse" on "Archive.org". However, it was directly by the hand of Treyarch that this channel was terminated as they have been known to send cease and desist letters to those who either obtain these dev kits or post media from them online. Multiple users have claimed that Treyarch has an automated tool to remove this type of media from the internet as it is posted.
There is without a doubt an early dev kit of the zombies game mode somewhere in circulation on the wider internet, and in fact Protype Preservation before their termination claimed to have a copy with early Green Run, even playing it claiming is was very different from the map Tranzit that we got at launch. This was said 3 days leading up to the termination of the channel, ergo the only footage of pre-alpha Green Run is now lost, assuming Prototype Preservation was served a cease and desist because of this claim. Since then several new pieces of photos/audio media have come up but no video exists of the early build online at all. Leaving the greater internet to wonder what early Green Run was like except the people holding these dev kits.