Adding local (cable) channels

I have put together a "rytec.channels.xml" like list with all the channels of my local cable provider.

What should I do to get Rytec XMLTV to fetch EPG data for these channels ?

One solution would be add these channels to the official "rytec.channels.xml", but if this has to be done for each local provider, the official "rytec.channels.xml" would grow endlessly.

Is there a clean way (surviving updates) to extend the list of channels with local channels ?