Unfortunately, the settings in distant_vehicle_spawn_parameters.xtbl seem to apply to ... distant vehicles, which means the fake vehicles you see out beyond the visibility range of normal vehicles.
I'm also looking for a way to increase the vehicle density and draw distance, but haven't seen anything misc_tables that would seem to do it. Was there an increased vehicle/ped density mod for SR2? If so the mechanism would likely be the same.
There are some files like "spawn_info_categories.xtbl" that likely have something to do with which things spawn where/when, but editing anything in here would be a nightmare... and you would think there would be an overall density setting somewhere. The view distance stuff might be harder, as it's entirely possible that's coded into the graphics settings (in display.ini it mentions that one of the settings controls draw distance).