Yes, it's such an obvious thing that it has been used in plots for movies/books for a long long time. Maybe the particular thing that causes the derailment or the specific thing that released is slightly different, but it's not like nobody has ever thought this as idea. In fact, some version of the plot that proves the idea is so believable is that they stage an accident and tell people it is hazardous to get people to evacuate to not see what's really going on.

The fact that someone could say this was unforeseen with a straight face should immediately put them in the nominees for whatever acting award show of your choice.