Amateur accident reconstruction time here. Assume the bus was going the speed limit, 100 kph. At that rate, it travels about 90 feet per second. And it might take, what—four to eight seconds or more to stop from that speed? So if the bus driver saw the truck in or near the intersection, the bus driver would have had to hit the brakes perhaps 500 feet or more in advance—a long way away—to stop at the intersection to avoid the truck.
In my mind, proceeding through an intersection at that speed, without stopping, and with trees blocking your view off to the right for all but a short distance at the intersection, is courting danger. Why do you think so many trucks and buses have decals that say “This vehicle stops at all railroad crossings”? Because it’s dangerous not to, that’s why. I, personally, blame the intersection for not having a four way stop. It’s one thing to have only a two-way (not four-way) stop on a slow road (60kph, for example). It’s another thing altogether to allow cross traffic when you are going too fast to stop. I can’t think of a highway anywhere near where I live, that allows cross traffic to enter from the side when I am going highway speeds.