We have to assume they aren't all one team =\ so mafia will still join in when voting for a scumnag from a different group.
If the count is right and there are 9 scumnags, it's very likely that there are different mechanics for the night kill. We can't be certain if it was or wasn't the vests, roleblock, protection or even the mafia abstaining or not being allowed to kill. It could be a votes only game which would be quite interesting. It would be hard for players to vote along with their team without it being too obvious they're together...