If you bought RW through Steam then, yes, you will automatically download updates (unless you specifically turn it off).
"Just post some random unrelated text. We have members here who can help you with that." ~ Chacal "When all else fails, read the instructions... if that doesn't work either, try following them." ~ Old Prof The Grade Crossing - Atlanta North Project - Virtual Rail Creations
Yep. From your Steam-client, games Library, right-click RailWorks, Properties, Updates tab, select "Always keep this game up to date" in the drop-down choices.
RailWorks Route & Scenario addons, video tutorials and other resources at http://www.RRYard.com