I just checked this route.
Here are the needed assets:
Essential: route won't be playable without theseRSC\HorseshoeCurve : Lots of scenery, tracks, etc. Payware DLC from Steam "Horseshoe Curve Route Add-On".
RSC\MariasPass : Lots of scenery, tracks, etc. Payware DLC from Steam "Marias Pass Route Add-On".
3DTrains\ScaleRail : Tracks. Freeware or payware from 3DTrains, everyone should have this. Also get Scaleroads.
http://www.3dtrains.com/products .
Important: route will be playable but missing items will be noticeableRSC\NorthEastCorridor: Lots of scenery. Payware DLC from Steam "Northeast Corridor Route Add-On". Includes APStation scenery items.
RSC\ShermanHill: Lots of scenery. Payware DLC from Steam "Sherman Hill Route Add-On".
RSC\DonnerPass: Lots of scenery. Payware DLC from Steam "Donner Pass: Southern Pacific Route Add-On".
Thomson\EandG: Scenery items and sounds. Payware DLC from Steam "Edinburgh-Glasgow Route Add-On".
Desirable: You may notice missing buildings and you will miss out nice features3DTrains\SceneryPacks : Trees. Freeware from 3DTrains, everyone should have this.
http://www.3dtrains.com/products .
CaptainBazza\Nautical: Great ships. Included in the free DLC from the RWA library "Industrial Interactive Route for RailWorks, version 4" .
G-Trax\PortlandTerminal: Buildings and scenery. Payware DLC from Steam "Portland Terminal Route Add-On".
Kuju\RailSimulator: Scenery items and sounds. Payware DLC from Steam "European Loco & Asset Pack" but included in many routes. If you have Railworks or Train Simulator 2012, you already have the contents of this pack.
Kuju\RailsimulatorUS: Scenery items and sounds. Payware DLC from Steam "US Loco & Asset Pack" but included in many routes. If you have Railworks or Train Simulator 2012, you already have the contents of this pack.
RSC\APStation: Scenery items. Not available separately but included in many routes, such as NorthEast Corridor, Falmouth Branch, Doncaster Works, Woodhead, Western Lines Of Scotland, Settle & Carlisle, Portsmouth Direct, WCML North.
Not important: some scenery items you won't noticeDeveloper\Addon: Clutter. Possibly default, everyone seems to have these.
GreatNortherner\Allegheny: Clutter. From one of numerous freeware and payware on Michael's "Golden Age of Railroading" web site at
http://www.stephan-michael.de/railsim/index.html .
GreatNortherner\GNRy: Clutter and streetlights. From one of numerous freeware and payware on Michael's "Golden Age of Railroading" web site at
http://www.stephan-michael.de/railsim/index.html .
RSC\BathTemp: One light. Payware DLC from Steam "Somerset & Dorset Railway Add-On".
RSC\CajonPass: One light. Payware DLC from Steam "Cajon Pass Route Add-On"
RSC\F40PHPack01: One light. Payware DLC from Steam "Amtrak F40PH ‘California Zephyr’ Loco Add-On"
RSC\HageSieg: One light. Payware DLC from Steam "Ruhr-Sieg Route Add-On"
RSC\NewcYork: One light. Payware DLC from Steam "East Coast Main Line Route Add-On"
Wilburton\Stockton: Some scenery. Wilburton\Stockton buildings and vehicles by Steve McGowen, available at uktrainsim.com. Included in the freeware WIP route from the RWA library "Sparks - Reno ".