Interesting! Sevastopol is so beautiful and intricate I'm always sad we do not get to just peacefully walk through it for the sake of atmosphere and its sheer beauty.
The mod actually does not trap the Alien, it just freezes it in place. And since it generally "spawns" in the shafts, well, it stays there forever.
Trying to find a PS3 version of the removal tool but no luck so far.
