Help creating 3d line and 3d background in Motion (WITH SAMPLE CLIP)

You should try to get in touch with Andrew Ramsay (who created the video) and see if he would be willing to share his project file with you. There's so many different ways to try to approach something like this, and the video really doesn't last long enough to get more clues.

One way to create the "main" line is to create a small circle and Replicate it.

Start with a Circle between 11 and 12 Radius. Add 6 Feather and 100 Falloff.

Here's the Replicator settings I used:

I also added a Glint filter:

To create the background "lines", I started with a Rectangle:

Width 14

Height 780

Feather 5

Then created a long line:

Point 1: X -23887.7 Y 0

Point 2: X 2413 Y 0

Then set the outline properties:

To make multiple copies of it, I used a Clone (for the example above) - but you can use as many clones as you like.

The different shapes (main line, background lines) need to be set up in Layer order, but their Z Position values can be "emphasized" to make the separations between them more visible.

Here are the Transforms (and other Properties where used)

For Camera:

For Main Line Replicator:

For background lines 1 (main Line shape)

For background 2 (clone of background lines line)

Once you get everything set up, you'll want to animate the Main Line from left to right on X and you'll want to animate the Camera orientation.

Hope this gets you started... but check with Andrew Ramsay too.