The method I've used here is using the same principle for both. A 2D plane for each video, one laid just above the other and the camera looking straight down.
Note: Both are rendered using OpenGL, not Blender's internal render.
With the split screen an 'inviso mask' face was added to the lower edge of the white line. (thin rectangular plane laid just above the video planes) The line was simply rotated.
(inviso mask - plane with transparency set to 0.008)
In the torn or jaggy edge version, a single plane was used and textured with it's video. A jagged edge (vertices) was cut into that using the knife function. That was then duplicated (SHIFT-D) and dropped a little under the first
At the opening frame, only the top plane and video can be seen until reaching the frame where shape keys INSTANTANEOUSLY fold the respective outer edges of each plane downward and underneath. (hinged at the jagged edge)
In this example the left side of the top plane, and right side of the lower plane are folded down at the exact same frame that we start to rotate (tear) both planes out from the bottom center. (origin point set to the cursor which is already set to bottom center)
Twisting the planes in the Z axis on the way down can enhance the effect.
Underneath both planes a 3rd can be added as shown here textured with our favorite movie studio pattern.
Both Blend files are attached and compressed. VE5 (the 2nd) the straight out split screen, VE4 (1st) the torn screen.
If as you mentioned, you're still needing video footage as to how it was done that can be organised. (hasn't been done yet)
The Blender files: (You'll need to substitute the original videos with your own)
Note: Rendering used OpenGL, not Blender's internal render.
Thanks also to @3pointedit. That could be another solution for you to try.