Duplication of minecarts

It's possible to get duplicate minecarts on a track by letting minecarts go in and out of loaded chunks. Problem described in this video:
https://www.youtube.com/watch?v=17W1vows9nw

Download of the world: https://docs.google.com/file/d/0B4TrJIjkwdYzbnZ1X1V3SGhhcGc/edit?usp=sharing

Position of the track: x=-2400 z=1600

Place a player in creative mode in a Minecart on the track. Place 2-4 Minecart on the tracks with various animals. Make sure no other player is causing any of the chunks involved to be loaded, i.e., all other players should be at least 200 blocks away from any part of the minecart track. Let the system run for a few hours (and make sure there is both day and night).

I should also mention that I have experienced this problem in the past as well on the 1.6 snapshots and single player world. But this was the first time a was able to reproduce the problem more than once.