Operators can any how add SD channels they can't pressurize for HD even if they bring HEVC this and that.
They cant pressurize for hd cahnnels, and they dont need to. Broadcasters will anyway add hd channels for the sake of competition.
But for those channels which are already in hd, if the dth operators stop adding their sd versions(since they show the same content as the hd version), the sd version will shut down eventually, and the useless concept of mirror feeds will be past.
In simpler terms, till a channel is not launched in hd, it is available in sd, but once it launches its hd version, dth providers should stop carrying its sd version and carry hd only....