Alright, but what's the intended use then, just an in scene path to grow Ivy?
Any change this idea can be picked up to 'convert' the imported spline into a painted line so it behaves the same (and can be extended with more paint and moves with the surface object?)
I tried working around it by linking the ivy to an object in order to get it to move, but that also doesn't work ... it's as if it uses an internal reference to the imported splines position/vectors etc with no way to access it after import.