Do cards in zombie spoils exist multiple times in the deck? For example, if I have the Moscow card in Classic would that mean that nobody else would draw it as long as it's in my hand?
I'm sure you'll find that providing the number of players x5 = less than the number of board territories, then no-one can have the same spoil twice.
In other words on Classic, in anything up to 8 players you'll be fine. If everyone's built up 5 spoils in 9 player however, then three territories will have been dealt out twice.