Marc = yeah, I'm pretty familiar with ATBA
Working BCs on out of site stuff means 'sending them over the next hill (or three hills) to lift the sheep. It's not really comparable to tending unsupervised- the jobs are really different. I've only worked a little with BCs, started out with one GSD (who we didn't take as far as we wanted for a variety of reasons, but did a LOT of studying and listening and learning from folks in the process), and most of my herding experience is with driving breeds who are mostly companion/show bred. They train REALLY DIFFRENTLY, especially on out of sight stuff.
I do think tending dogs are vastly underutelized, especially in large open range situations, but I think an awfully large amount of farmland is too close to roads/fields too small for tending dogs to be used to best advantage.