They are taking a route through a mix of the geography in the area --- that should be a beautiful ride. As I remember, none of those hills are much to worry about if you have any climbing legs. And, as you turn onto Cassel Road at about mile 43 or so on the map, Clint Eastwood's ranch is to the right where the lakes show on the map. I think he bought the property from Bing Crosby. Only worth noting because there are some killer large rainbows in the lake that spawn in Hat Creek and make for some fun fishing at the right time of year.
Anyway, the western part of the ride has more trees and the more east and north you go, then it becomes more farm and ranch land (this is where you get some great views of Mt. Shasta). And, when you are done for a true cross-cultural experience, stop in at the Buckhorn Saloon in McArthur. You might be careful about the lycra in there or at least wear some cowboy boots with your bibs.... Anyway, that should be a very fun ride.