This technique was used in Paragon, and mentioned on the “Foliage & Parallax Occlusion Mapping Techniques used in Paragon” live stream.
The best summery I can find on how to use it is here: Sprite model? How did they do this? - Content Creation - Unreal Engine Forums
The wiki isn’t much help WorldPositionOffset | Unreal Engine Documentation
Here is the result I’m getting after playing around with it for a few hours, the spline is facing the camera correctly now after A LOT of trial and error, but the shading is completely messed up, even after playing with all of the extra settings: http://i.imgur.com/GnDSP2s.gifv