The albula line's maximum gradient is only 3.5%. The 7% sections are over the bernina pass down into Italy (tirano), where trains are generally pulled by double headed railcars. There is a 6% gradient on the Chur-Arosa line. I noted a little while ago that they're planning a new tunnel bore on the albula pass as the old one isn't in the best of condition. Fortunately this will only be a parallel bore to the existing one (only 6km long), rather than a base tunnel type project like the gotthard and lotschberg ones. Remember that the RhB built the Vereina Tunnel (20km long) in 1999. If you invest in your rail infrastructure, funnily enough it can do an excellent job of transferring millions of passengers and cargo which would otherwise ruin the landscape on the roads. I imagine graubunden's economy benefits hugely from the amount of tourists who come just to see the railways anyway!