While poking around in the CK in the Tamriel worldspace, I found several strange objects outside of Helgen.

In addition to the normal bounding box around the mesh, there were long green lines extending in one direction from the mesh. (Most trees, rocks, and other meshes in the immediate area also had these lines.)

Here's an image of one of the http://i.imgur.com/koAaB.jpg

What are these lines exactly and what do they do?

Looks sort of like an object attached to an Xmarker for enabling/disabling purposes, but without pulling it up I'm not sure. (I don't know why you would enable a rock that way, lol.) Check the Enable parent tab and see if it's enabled by a marker.

EDIT: I just figured out where that was by Helgen, right? My guess is that it's enabled after the intro sequence and the player escapes into the world.

Thanks for the info!