Especially in the US even a fairly simple "hybrid" self driving truck could probably provide some savings. Automate the long straight roads and let the driver take over for everything else. Depending on the route the sleep schedules could be met during the automated driving part. I guess that's what they meant with the sentence about saving 50kk/year even in the current form.
As an aside, the article mentioned that the driver was sleeping in the back...I'm sure that's no accident. However I doubt that's a safe thing to try (and only possible in these very artificial circumstances) even with a good warning/wakeup system in place it takes too long to get from the back to the front and react.