Zeh has posted a great article on using Tweener to animate along a Bezier. There is even a papervision3d sample. Tweener has been a good choice for papervision3d animation due to its flexibility to be able to easily handle z and custom params.
This is excellent for game development or pathing in game systems. The sample in papervision is a set of cones that the path can be set around. For custom scripted sequences and triggered events this is exactly what is needed. Things like flying through cities, vehicles, transitions, recording replays etc.
I will give this project 6-8months before its a full blown papervision3D scene editor in flash.