> > #2): In many cases, many AM stations aren't allowed to use IBOC at night.
>
> AM analogue is like that too, isn't it?
Not nearly to the same extent. Some AM stations must lower power, change directional pattern, or sign off at night, but many more of them who don't have to do any of those things still have to shut off their IBOC due to the adjacent channel interference with nighttime skywave.
An example is WBZ here in Boston. It's authorized to run the same power and pattern 24 hours, but still must shut off it's IBOC every night.
WMKI here in Boston also runs the same power (though with different patterns) 24 hours, but must shut off their IBOC at night.
I don't know how many NYC AM's broadcast with IBOC. I know that WOR does, and they must shut theirs off at night as well.
WABC does not (yet) run IBOC, but if they did, they would most likely have to shut it off at night as well due to adjacent channel skywave interference issues. That would mean that in winter months, this new Saturday evening oldies program would not air on the IBOC at all. In the summer, perhaps a couple of hours of it might air on the IBOC before sundown.
However, if WABC was broadcasting in analog AM stereo, the oldies program could be heard in stereo sound almost as good as FM stereo on wideband analog AM stereo receivers within their primary Greater NYC listening area (and wherever else they cover cleanly), and the entire northeastern U.S. could hear it in AM stereo (though not as cleanly) on the skywave after sundown.
With IBOC, assuming that I'm correct that they would have to shut it off at night, only a couple of hours of the show could be heard in stereo (and on HD radios only) during certain times of the year, and not at all at other times.