Unreadable BMP files

Yesterday (for me), I saw a Le717 and a few others discussing the strange .BMP files in Lego LOCO. I asked for a file to try to open, and it was sent. I spent some time poking it, and came up with some interesting info.

Here's the header stack of a normal .bmp, when viewed with a hex editor:

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Here's the headers from a mysterious file, found in /trains/carriage1/car.bmp:

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This isn't all I've found. I took a look at duck.bmp, which is one of the openable files. It shows several views of the duck sprite. It has the normal headers (which is why I could open it)

Each .BMP, readable or otherwise, has an accompanying .DAT file. The trains follow one format, while the animals follow another. Here's duck.dat's filtered hex for reference (the animal .dats are the most complex, and show how the file works)

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QUESTIONS I HAVE:
What happens when we add a header to the unopenable .BMPs?
Can we substitute a readable .BMP for an unreadable .BMP, and still have it work?

ON A SEMI-RELATED NOTE:

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I tracked down the devs. Matthew Stibbe, the founder, was the developer on LOCO. Maybe something that can open their in-house files can help? Maybe a tool for opening the Stunt Rally textures can help here, or a tool for Dune 2000 (same dev, same year as LOCO)?

UPDATE ON SEMI-RELATED NOTE:
I found Matthew Stibbe. He's alive. He admits to working on Loco as head designer.

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HERE IS MY COPY OF THE FILES:

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