Hi there! I'm using different folders (of TaD LEP) for lights and cab views, but that doesn't matter.
So far, as you mentioned, and is stated in Readme.pdf, only the 3 default engines of each pack have the lightings enhancements. Tomorrow will be include all the other liveries in the Expansion Pack.
As I use to do, I also downloaded the pack from RWA and installed it in one of my \railworks clean installation (only default and DLC packs) and it worked flawlessly. If you followed the installation instructions (the "Extract here" is very important, for many users), the only clue I can give is that lights and cabviews folder is placed within \Kuju\RailSimulatorUS folder. US Routes (in which is supposed the engine will be used) have as default (in the blueprints provider/product flyout) Kuju\Railsimulator checked.
Test Trak route, for example, is a UK route, the pack won't work for lightings and cabviews untill you check the Kuju\RailSimulatorUS box. I installed the pack (again, for testing purposes) and created sample scenarios in BSB, Castle Rock, NEC and NERW and had no problem.
Let me know if you got it fixed.
And more... if you verified game cache you have to re-install the pack, or you won't hear even the new engines sounds as well.

When you set TSX on, can you see the headlihgts? If not, your ...\steamapps\common\railworks\Assets\Kuju\RailSimulatorUS\RailVehicles\WJDoc folder was not correctly installed, and probably due to problems when unzipping the pack.
Cheers,
Doc.
Edited later: I've been hearing that you have to run RW_AssetSetup.exe as Administrator (Win 7 users), otherwise you'll get a deffective installation. I don't know because in my pc I ran all the programs as Admistrator by default.