I do not disagree that PBS should and within 3 years will be available in all markets in HD. What I am saying is that if they uplink WGBH, they will need to add WENH and maybe others, whereas if they can cleanly add only one PBS HD - to serve and complete a DMA, it might be easier to do so. I do not know how full some of the spotbeams are getting for HD in major DMAs.
I agree PBD HD would be the best way to go for the interim. However, the PBS stations, though public and non-profit, are acting no different than their commercial cousins. They do not want competition. In this case, those who watch PBS HD will deny the local pBS stations from bombarding you with auctions and pledge drives. They cite local content and news, but it is really about the money.