Re-reading this last night I thought, no Batchelor, they have Westbrook observing Western Union from a second-floor window and Ruby parking and going in, possibly waiting until he came out and headed to the back door. Then going back up the adjoining stairs, past Fritz office signaling him on the way by that Ruby was on the way.
Then I thought, this is not mutually exclusive to Batchelor escorting Ruby. If he was in the basement attending to the armored car, he was in close proximity to the parking garage and the service elevator in it. If word was also passed down when Ruby arrived and parked with a nod or tip of a hat could have alerted Batchelor to walk to the elevator, go up one floor and be there to greet Ruby. Getting there might not have taken 2-3 minutes. Plus, likely Croy was guarding the elevator then also escorting them to the point where he and Ruby joined the crowd as Batchelor went on. Croy is seen clearly in pictures by Ruby as he steps out to shoot Oswald.
Anyone really interested in this aspect should take the time to read this article and look at the pictures and diagrams. If you don't buy the Harvey and Lee story, or even part of it, fine. This is not about that.