Note CBS is an unencrypted broadcast television provider. No copy restrictions can be imposed.
But, there is nothing requiring CBS to allow Dish to retransmit their signal. In fact the satellite television act says CBS can either force Dish to carry their channel (must carry) or charge if they want. It does not put restrictions on terms and condition of what the broadcaster can charge. As a condition of carriage CBS could insist that Dish or Dish's equipment in no way automate commercial skipping. Dish could manufacture an OTA box which the customer could use and that box could skip commercials and CBS would have no recourse since the signal was received OTA.
Already being done. The USB OTA tuner will record their OTA signal, and it has been reported that with PTAT on, even minimally, that AutoHop works on programs recorded OTA.