When summoning or spawning a LeashKnot entity (the entity which corresponds to leads tied to fences), the game will always create it at the coordinates 0, 0, 0, regardless of what data is specified for it.
For example, you can use the following command:
That should spawn the entity at your current coordinate, but will instead always spawn it at 0, 0, 0, regardless of where you use it.
Similarly, LeashKnot does not accept any NBT tags, so this does not work:
Again, it will instead spawn at 0, 0, 0.
Finally, this bug also effects LeashKnot spawners: regardless of the specified coordinates, the knot always spawns at 0, 0, 0. See the attached spawner schematic if you wish to test that.
EDIT: in 14w11b, the LeashKnot's coordinates are a bit buggy. They seem to render at the specified coordinates, but act as though their real location is 0, 0, 0. If you are not looking in the direction of 0, 0, 0, it will not render at all. In addition, it responds to hits at 0, 0, 0, rather than its apparent location. It also uses the given coordinates to determine whether it is on a fence.