The FCC is considering imposing mandatory carriage for all subchannels
> ("multicasting"), but it hasn't taken formal action.
At least in market #6, all of the stations which have an interest in doing so seem to have managed via retrans consent, and all are available (HD and subchannels) in the clear over the Comcast system I was able to check. (They are however remultiplexed and I suspect some may be recompressed.)