cdbcorn said:
Is that really the issue? Why would PBS charge for carrying the HD signal?
You mean why would PBS charge D*?
Because they can. They perceive that the customer sees their service as of value and therefore it will increase the value of D*'s locals service. So they try to get a piece of the pie.
For a while analog channels played a similar game with carriers. They had two choices, either force D* and cable operators to carry their channel ("must carry"), or try to extract money or value from D*/cable while running the risk of the carrier opting not to carry them.
One big time channel in the SF Bay Area, KRON, forced Bay Area cable operators to carry another channel they were starting, Bay TV, in exchange for being allowed to carry KRON. That failed and shortly thereafter, KRON made a power play on NBC and lost, now they are a rather small-time independent channel.
The FCC didn't make "must carry" an option for the digital variants of stations for various reasons, some say the biggest reason was that carriers didn't want to be forced to carry local stations with no perceived value (like ones to turn all their air time over to shopping networks).
It is unclear to me whether "must carry" becomes an option again once the digital cutover is completed.