I dug on google and found nothing for importing or exporting the .maps. My googlefu hasn't been up to par since they changed their algorithms earlier this year, so I may have missed it.
For now, doing it the hard way. Starting with a complete grid of 20x20 checkerboards of alternating colors, then counting pixels, and adding lines, until I've found the exact bounding boxes. Then creating a nice, layered image file. So much harder than it has to be, but hey, its working.
Any word on those textures that had that public domain like license?
Also, how high priority are replacing !(x^2) (non power of 2) textures?... I'm finding a handful in the unknowns that are like 160px, or 48px, etc.
In my hard-way mapping textures, I'm doing it WITH converting to ^2 textures, so that a 160px becomes 256px, 48px becomes 64px, etc. And yes, verifying everything in radiant first to make sure they match the prefabs.