Extracting icons from CE1.0 exe files

For my ongoing archiving efforts, I'd like to be able to automatically extract and convert icons from exe files.
7zip can extract the files out of the .rsrc/ICON resource, but what I end up with are several files that the linux file utility identified as DIB (Device Independent Bitmap) files.
ImageMagick has an decoder for DIB, but it doesn't work with these files. What I assume is that these are 2-bit DIB files, just like .2bp files are technically bmp files with a nonstandard 2-bit depth, these are probably just DIB files with a 2-bit depth that no software can really handle.

So the question is, does anyone have an easy way to convert these into other formats? I don't fancy writing yet another decoder

Have you tried opening them as .2bp files on the device to see if they are literally .2bp files? Do they even have alpha channel information?

No, they're not 2bp files. Considering it's identified as a DIB file, and DIB files, like bmp files, usually have either 1, 4, 8, 24 or 32 bit color, I'm pretty sure this is a 2-bit variant of DIB that no software can handle. I haven't found any tools that can handle these files, so I might have to write one after all.

From what I can see, they're

RGB(0,0,0), RGB(132,132,132), RGB(198,198,198), RGB(255,255,255) + 1-BIT ALPHA. So it must have a secondary alpha table mask.