Scanning the site see mostly points algorithms, the only mention of polygons is a textbook LibGEOS call, I see no network at all. And I see no smart manipulation of anything else than points, I see no subdivision of space, etc.
I have worked with it. It was just stating, very little useful code in it. Going back to the source code, I see they added a bit more.
A quick look around suggest that only one algorithm uses an indexing structure. Clipping seems limited between a convex polygon and a concave one.
