We walked off the plane at 11:45pm a couple Fridays ago and were in our ME resort line by midnight. There were probably 80 people clustered in mostly 5 lines by then, and maybe 1 other group got into any of the lines after us. However no buses were waiting outside

. Waited another 20 minutes and all of a sudden several buses rolled in and were quickly loaded, on our way by 12:30 am. Our bus was filled BUT there were 5 stops.... no doubt this was the last major surge of incoming guests and they were doing it with a few buses as they could. We were the 4th stop (Coronado, AK Jambo, Kidani, Sports, then either Animation or Music I think) and close to a dozen get off there. The previous stops had only 2-3 people get off each time. Got to our room at 1:45 am.
So if you come in late, be prepared for some time touring the various resorts late at night. Now I know what is shown on the video screens when you go through the entire loop of ME intro and Disney shorts - it reverts to a screen that just shows "Magical Express" and no music