1. Turn off the R option for the BeautyPass layer and turn it ON for the Wireframe layer.
2. In the Render Options choose May Vector. If you do not see it in the list, go to Window > Settings Preferences > Plugin Manager and check the box next to VectorRender.mll. You should now see it appear in the Render options window.
3. Choose the Maya Vector tab.
4. Under 'Edge Options' check the box for 'Include Edges'.
5. Set Hairline and Edge Weight to preference but leaving them set to default works very well.
6. Edge Style should be set to Outlines if you want Quads to show. Changing it to Entire Mesh will give you triangles.
7. Change the Edge Color to anything but black. White works well since you can change the color in After Effects or your favorite compositng program.
8. Close out the render settings window.
9. Right click over your model and choose Edges then select the entire object so that all of its edges are selected.
10. Under the Polygons Menu Set choose Normals > Harden Edge - this is what lets you render the entire wireframe. Not doing this will cause it to render only an outline around your model, kind of like what a Stroke does in Photoshop.
Next, important!, In the attribute editor view the attributes of the Shading Group that your shader belongs to. Not the shader itself! Its SHADING GROUP. In the AE view of your Shading Group expand the mental ray section. Then expand the Contours section.
Check 'Enable Contour Rendering'.
Select your Colour, Alpha, and width you want your wireframe lines to be. I chose Color:white, Alpha:1, Absolute Width, Width:0.5
Open the render globals window and go to the mental ray tab. Expand the Contours section. Expand the Contours->General section. Check 'Enable Contour Rendering'. Expand the Contours->Quality section. Set Over-sample to 3 (this makes the lines smooth/anti-aliased) Expand the Contours->Draw Contours section. Check 'Around All Poly Faces'