Quote Originally Posted by Spur
isn't that last listing just descr_regions.txt revisited, in that exact same order?
That's what I was thinking - but here's the real question - why?

And it's clearly not isolated behaviour, it does it for both the regions and for climates. Presumably it does it for others as well (more testing may be required).

Sadly, it doesn't answer the question that I set out to answer in the first place - what on earth does it take to add new provinces to the campaign. I would guess there is something new to imperial_campaign_regions_and_settlement_names.txt that we just don't know about (or the game is nice and broken).