After reading Tom's latest update, I think I will retract the bit about the driver needing to be more cautious, and blame it instead on the camera playing tricks. But as a pedestrian, if it wasn't clear which way the sirens were coming from I might have walked a metre or so out onto the crossing, just enough to see round the bus, and then checked the ambulance wasn't coming my way before proceeding. (I don't know about that particular area, but certainly in the area I frequently walk around, there are numerous roads going parallel in different directions separated by only small distances, and it is often very difficult to tell which way (or on which road) the sirens are moving.)