They're all connected to a single virtual reality. Bascially, the Astraeus crew members have all been plugged into The Matrix. Also, regarding the time-travel comment, even if what we saw really happened and wasn't an artificial VR construct, that wouldn't really be a "Time Travel" story in the same way their trip to the 1940's was a Time Tavel story. This would be more like a Rip Van Winkle or Buck Rodgers story. But in any case, the amount of time that has elapsed between the Astraeus being lost and us seeing Beverly running the Matrix is almost certainly not four years. It's probably a minimal amount of time at this point, like days, maybe weeks tops.