I read thru this post & my experience is that Comcast by me did not implement PSIP on all channels at the same time for their QAM HD stations.
My Sony TV gets still gets these at their real channel numbers in the 100+ range.
My Panny DVD recorder originally got some at the same channels as the Sony. However a couple were mapped to their VHF channel numbers on the Panny. IOW they were split up. Then last month I could not get the real HD QAM channels on the Panny. Just were not there one evening. A new channel scan found the "missing" QAM channels and mapped them to their equivalent VHF channels. Or thereabout. But the Sony keeps getting them at their original QAM channels.
I said thereabout because two channels were mapped to a ".2" instead of the usual ".1" number. Also one of my PBS subchannels is at 1.4. It probably should be 11.4. So obviously Comcast has the ability to modify the PSIP info and map wherever they want to.
My 2 QAM tuners are behaving differently. The Panny will only receive digital channels that were picked up on a channel scan. And once it detects the mapping signal it stores this information and also prevents you from manually entering a non-detected channel. I cannot get 116.1 anymore on the Panny. It must be saying that it detects PSIP on 116.1 and locks me out. But when I enter 2.1 it does tune in the real 116.1 signal.
I have not redone a channel scan on the Sony for over a year. It still does get all my local Clear QAM HD channels in the 100+ range. 116.1 is CBS. However I do not get CBS mapped to 2.1, probably because I've never done a new channel scan since Comcast presumably started using PSIP. But the Sony lets me tune in any real available channel there is, so I'm reluctant to do a new scan.
I would also think that if one tuner picks up Fox19 on subchannel 19.1 then another QAM tuner connected to the same cable would also pick it up on 19.1. That is presuming both did a channel scan & received the PSIP info. But if they are still different, it sure is a mystery.