Hi,
Actually - voting leaderboards are implemented via the PostScoreToLeaderboardOnBehalfOf() call - where you can basically vote for someone else's score. [i.e. voting for that person].
Create the leaderboard as a "Cumulative" leaderboard - and basically the player votes for the score of another player - incrementing it by +1.
I suppose we should add those details to the roadmap item!
I hope that helps to clarify things!
Paul.