Maybe the cards will detail this, but I'm a bit confused with the wording.
Special zombies are randomly placed [with a die roll to one of the 6 locations].
If the rolled location is:
- Filled with zombies -- special zombie is not placed
- Barricaded -- special zombie is not place; barricade intact
- Explosive trap -- special zombie not placed; explosive trap intact
Is this correct?
According to the rulebook (page 18), if you cannot place the special zombie(s) (because of the reasons you listed), it triggers the same effects a normal zombie would. So
- Filled with zombies: Special zombie is not placed, but the location counts as being overrun (kill the survivor with the lowest influence in that location).
- Barricaded: Special zombie is not placed, a barricade is removed.
- Explosive trap: Special zombie is not placed, remove a trap token, remove all the zombies that share the entrance.
Also...if there is a Bandit Leader and the crisis card indicate a location -- that location is ignored in favor of the Bandit Leader's choices.