Timewarp never has had any option to use external motion vectors, so the whole approach makes no sense. You completely misunderstand. You need Revision FX RSMB Pro.
I apologise for creating a question that appears to make no sense. Although your assuming I have not considered RSMB I can assure you that it was the most obvious choice to take, but is also at the cost of a one off and annual expense. I'm assuming other may jump to the same conclusion, so to avoid this I should point yourself and others in the direction of the after effects help section about timewarp using the following link
Refer to the time warp section, and look under the heading 'Warp Layer' you will find the following sentence
"Warp LayerAllows you to warp the layer to which the effect is applied by applying the motion vectors from the layer that you choose."
Now unless this is out of date, it's pretty clear in stating that motion vectors can be used in the timewarp effect which is what lead me to asking the original question.
Has anyone had any luck with exporting motion vectors from 3ds max and using timewarp, warp layer, to create motion blur?
The warp layer uses the motion of the pixels in that layer not a 3D vector map. Different idea entirely. Experiment with the effect and you'll see what it does.