This is my thinking as well. We need to build for the task at hand not try and integrate into what we already have. The first sentence in this article is where the failed assumptions are.

  "Trucking was supposed to be the ideal first application of autonomous driving. Freeways contain predictable, highly structured 
  driving scenarios.."

When sharing the road with human drivers this statement makes no sense as all. Vehicle's are their own entities with no connection to each other outside of the road, signage and defined lanes. Instead of trying to build sensors for a existing 8-lane highway just do it for (2) isolated lanes. You don't have to plan for 100% of human scenarios if they are mostly removed. We don't fly airplanes adjacent, behind, ahead, etc of each other why is the assumption that autonomous trucks need to be on the same road as everyone else.