They call me Mister...
However, players may still run out of miniatures of the indicated type when required to place a Zombie on the board (when spawning, populating a building, or due to splitting). In this case, the remaining Zombies are placed (if there are any), and then all Zombies of the requested type immediately gain an extra activation.
I read that as simply one extra activation for running out of minis no matter how many locations require the mini of that type.
EDIT: By the by, I would see it as one location i.e. the sewers (manholes) anyway.