If you go into the Options > Television > Edit Channel List you will see that there are a channel "Name", "Channel Number" and "XMLTV Identifier".
As long as the channel "Name" and "Channel Number" stay the same, which is within your control, and you simply edit "XMLTV Identifier" to match the new incoming XMLTV Identifier in your XMLTV file, then nothing else should change in MC. Subscriptions are tied to the "Channel Name", so if your existing channel name is "1007 KABC-DT", and the new name in your XMLTV file is "KABCDT", then just put "KABCDT" into the "XMLTV Identifier" for channel "1007 KABC-DT". (Okay. I prefixed the "Channel Name" with the channel "Number" because I see you do that in MC, as do I.)
Then theoretically all your subscriptions should work as usual without being redone.
Which XMLTV source are you moving to Muzicman0?