Looks like it could be different for satellite folks, but certainly not a BS statement being that I was talking from a cable/FiOS perspective.. MSG-HD and MSG2-HD almost always (if not always) show the same broadcast for Rangers and Knicks games, even if the Devils and Islanders are playing (thus pushing one team to MSG+HD and the other to MSG+2 which is standard def on many providers outside of Cablevision)
Let me show:
Exhibit A - The Rangers game tonight is clearly on both MSG-HD and MSG2-HD (though this TV listing website gives MSG2-HD a funky name). You can also see that, yup, even the postgame show is on both channels as well. I'd be glad to take a photo of this tonight on my FiOS guide as well, if you'd like.
Looking more into that MSG2Z channel, it seems to pick up most of the Sabres games. This channel might be made for Upstate NY and will show Buffalo/NYR/NY Knicks games. I think that is because regular MSG might be blacked out our used to be blacked out upstate.
MSG2Z literally is the same channel as MSG at all times except during Sabres games.
Exhibit B - On October 17th the Knicks, Islanders, and Devils are all playing at the same time. Would you look at that, the Knicks get featured on both MSG-HD and MSG2-HD (not given the proper name on this site either but you can see they are 2 separate channels). You can also see that the Islanders are listed as being on MSG+HD, as they should be for this game. You can't see the MSG+2 listing because this channel only becomes available when a game is relegated to it.
I would post images proving this for all of the examples I gave in the original post you tried to call out, but TV listings are only available so far out. Would be happy to add more images for future games as they become available.
You'll almost always (and really I'm 99% sure it's
always) see the same game on both of those channels. Only time that doesn't happen is when all 4 teams are playing at the same time, in which case it's Knicks on MSG-HD, Rangers on MSG2-HD, and Devils/Islanders a coin-toss between MSG+HD and MSG+2 standard definition.