Java 1.8.0_25 64Bit
With the snapshot, containing the Brigadier Command-System, it is not (easily) possible, to teleport (non-player) entities relative anymore.
I am aware, that the old behavior of the tp command is non-existent anymore and that
teleporting all entities (including yourself) above yourself is correct, instead of teleporting every entity up relative to itself.
However, doing this with execute is not possible either in the snapshot:
Which is in my eyes the way to do it, will give an error message, that a relative teleport requires a player to run.
Therefore the only possible way of doing a relative teleport on something, that isn't a player currently, is by summoning a temporary entity and teleporting to that.
In my eyes, it is a bug, that a relative teleport requires a player as an executor.