If I recall from past conversations about the MT story line, the security footage and lift hill audio is from "current" time, not from when the MVLCo was abandoned. The greeter position is a current day security checkpoint to keep people out, but some urbex folks have gotten in and security is going thru the woods looking for them. The urbexers either see security or the mystic item, find an old truck, and jump in (this is the audio that plays when a train is dispatched). Then the audio plays on the lift hill giving them a final warning to leave and if they dont, whatever they do, don't go in the shed!
I could be wrong about this, but this is my understanding.