Keep repeating yourself and keep quoting kinetic energy figures that are totally pointless to this thread, nobody cares about your .270 Winchester no matter how many times you keep telling us about it, the fact is I have seen low powered bb pistols shatter car windows with ease, specially the first shot, although a second in quick succession will obviously see the power drop off, thats all I'm saying dear.
The damage to the bus windows was just as likely to be pebbles, they act in a similar fashion to steel bb's and can be thrown by the handful using very little force and will easily cause that sort of damage, unless it was someone hidden in the bushes with a .270 Mannlicher.