Actually witnessed a horde teleport into the yard around my safehouse (the house in the southeast with the high, impassable fence. One minute, inside the fence borders clear of zombies, make another lap around the inside and suddenly there was a horde INSIDE the fence borders. Fence had not been knocked down, and they didn't come from the entrance, just magically teleported into the area when my back was turned. Needless to say, poor Jonny Noshoes didn't last much longer.