Here's a list of Developer folders & sub-folders that could now be considered "default" for RailWorks:
Kuju/RailSimulator
Kuju/RailSimulatorUS
GermanRailroadsRW/Hagen-Siegen
GermanRailroadsRW/Rollmaterial
RSDL/Foilage01
EisenbahnwerkRW/Rollmaterial
Castlerock/Scenery
RSC/APStation
Though, the RSC/APStation pack is a free addon, by RSC, that would have to be downloaded first:
http://store.steampowered.com/app/24086-----
From RW_Tools you can check to see if a scenario uses default stock or not;
Route Building Tools > Check Route or Scenarios, select a route & then a scenario from the list you want to check, then click on the "List items used by selected scenario" button. The list it generates, default stock has "Default Stock" at the end of the line, if it's non-default, it won't have that part added to it.