A whooping 110GB patch. About as much as the original game install.
A-life blin!!!
I know it isn't exactly how it is in COP, but it seems pretty damn convincing! They spawn in much further away and monster spawns don't just pop up in towns as much, forcing them to travel in.
I've seen the videos of people following NPCs and aside from a few areas where devs kill enemies to keep them from traveling like one or two bridges, they pretty much do just meander about.