Hi,
No, that's some very old historic thing, for having cobrand config in a separate repository I think it was, nothing uses that any more (looks like I removed it in 20113bad5b but missed that file).
On your original question:
* For GEOCODING_DISAMBIGUATION, yes, you can override what this is on a per-cobrand basis by adding a `disambiguate_location` function to your cobrand .pm file returning the data instead;
* For MAPIT_ID_WHITELIST, I'm not sure exactly what you're after here. I may well have missed something, but I don't think you need to have different values on a per-cobrand basis - I would put all the MapIt IDs you wish to be used in MAPIT_ID_WHITELIST, then you can restrict which of those areas a body covers using the admin interface.
ATB,
Matthew