It was real. From the story I read about this the bus drivers are given a schedule which told them what time to head out onto the track to pick up the marshals.
But apparently there was a red flag or something at one point that caused everything to be running late but nobody told this driver and he/she stuck to the schedule despite the F4 (I think) race still going on. There was also a secondary failure because a security person would've had to let the bus through a gate.
