This is an outgrowth of a thread a read a long time ago on RPG.net (which I will not link to, since I cannot find it). It discussed what would happen if a bunch of High-level Player Characters from a typical fantasy setting somehow came to our world.
In my opinion, I think the result would be complete chaos, involving loss of life and property destruction on a massive scale (i.e. standard PC behavior)
So, we can use this in a game. This time the characters would be the people investigating these events, and trying to figure out how to deal with the superpowered troublemakers that have suddenly appeared.
For a more interesting game, you can do this with two groups, one playing the fantasy characters, and the other one the modern ones.