Why would they move QAM channels to IP only under any circumstances?
If you look thru all the IP-channels, most were NOT "moved" to IP-only; they added HD versions of existing channels
to the lineup, in IP-only. You can still get the SD versions of those existing channels on your Tivo, as they are still QAM. I know you don't want to hear this, but that's not "moving" channels to IP-only.
Your local system might also be very strapped for bandwidth, which is why some of your existing QAM HD channels DID get moved to IP-only, such as WGN-A, C-SPAN 1, Cooking Ch & DIY. I do understand what you're saying re: moving existing channels to IP-only...but that's the reality of what's happening on Comcast. We still are getting them in QAM here just fine. Of course, that COULD change at any time as well.
Also, Music Choice did NOT get "moved" to IP-only in the Central Division; it's still very much QAM here & even still works on DTA boxes. (I have all 3 types of Comcast boxes besides my Tivo, & I leave 1 QAM box on MC 24/7 for the whole house, so I know this for a fact) If you cannot get these on your Tivo, you most likely have a channel mapping issue with your particular, local Tivo lineup, that might need to be fixed. And to that point, MC is probably one of the LAST group of channels that will get moved to IP-only, as they take up VERY little bandwidth to begin with. (the equivalent of 1 analog TV channel for ALL of them) If you know anyone that has a non-X1 cable box or DTA on your system, ask them if they still get MC & then you'll know for sure. (I can 99.99% guarantee they are...)
To be sure though, most (complete) new channel adds, are now IP-only; Hallmark Drama (BOTH SD & HD versions), Newsmax & Black News Channel are examples of new IP-only channels - & as already mentioned, are mostly fringe/2nd or 3rd tier channels. Also, depending on the contract that Comcast has with a given channel, they ARE still adding QAM channels here & there; we just got Marquee Sports added back last May, & BOTH SD & HD versions were added in QAM & work just fine on Tivo's here. (after rattling Tivo's cage to get the channels added to our local lineup, which they did)