What you can do is such a situation is this:
Go to the Wikipedia page for the network, for example
this one for Grit TV.
Find another affiliate of the network, preferably one in a very small market (they are less likely to preempt shows with local crap).
Look up that station on Wikipedia and find out where it is located.
Go to any zip code finder on the Internet and find a valid zip code in that locality.
Create a new directory temporarily (so you don't overwrite your mc2xml data) and copy mc2xml there and run it with the new zip code to create a new mc2xml.dat file for that directory. Rename the created mc2xml.dat to something like grit.dat. Also, examine the xmltv.xml file to find out two things: The exact call sign (display name) for the channel in question, from a channel block near the top of the file, and also whether there appears to be actual program data for that channel. If there is not, you will need to select a different channel from that network and repeat the above process.
Once you have a valid dat file for a channel with good data, copy it back to your original mc2xml directory (don't forget to rename it first!). Now, create a .chl (such as grit.chl) containing only the exact call sign (display name) of the single channel you want. This is so you don't get a bunch of data for channels you cannot receive.
When you want to get listings for that channel, use something like: mc2xml -D grit.dat -C grit.chl -o grit.xml
It will put those listings into a file called grit.xml. Now when you do your main run of mc2xml, you can use the -I option (I for "Import", not a lowercase "L") to also import the data from the other channel (mc2xml -I grit.xml .....). This should produce a combined mc2xml file carrying all the listings.
For the second station with no listing, if it also has a station carrying it in the same locality as the Grit station, you can just add its display name to the .chl file so you get data for both stations. Otherwise you can chain runs of mc2xml for different localities, always using the -I flag to bring in the data from the previous run on each successive run.
Don't forget to remap the channels in your backend and to delete any temporary directories you created.
Then you can check your local listings again in a few weeks, because sooner or later you may actually start getting valid guide data for those channels in your own city. Good luck!
By the way, there is supposed to be a way to get TitanTV data using mc2xml but it requires some kind of 30 character ID string that identifies your account, and no one, not even the creator of mc2xml, seems to know how to get that 30 character string. The search for that information is akin to the search for the holy grail!
Also by the way, I am amazed that you can get a good signal on Grit via FTA - they have one of the weakest signals I have come across in a long time!