There are two parts to the effect. Firstly the black outlines, which are done using LOTS of polygons. Basically the model has a duplicate of itself colored black and with flipped normals. This duplicate surrounds the original model completely and, because of the flipped normals, is only seen behind the original - thus creating the outline effect. Check out the honey.shader file to see exactly how it's done.
Honey is about twice the polycount of a normal player model.
They still load the geometry into memory, but do not draw it so the performance hit is almost halved. I hope someone else will take this technique and do a really low-poly cartoon character now that I've shown it can be done. This is one interesting model. He calls it an experiment and considering the polycount on this bad girl, you will need to be careful when handling her as her full count, she is about double a regular id model. So one of her equals two of a 'normal' model.