I recently discovered this peculiar archive:
http://www.triton.vg/TesseractRCPM+Catalog.html
Most of the files bounced everywhere and can be seen in many mirrors, but some are less common or perhaps the search engines can't locate them easily (such as a couple of (de)compression tools written in native asm code).
After battling a bit against RDMSDOS.LBR I discovered a little gem, the tool was compiled with Small C and both the source and the compiled programs are present.
The bios() calls are rarely emulated and can't be tested easily, but I could take note of the error messages of the z80mu trap routines and compare the existing program to the one I was trying to build with z88dk.
Now I'm confident that bios() works correctly, even if I never could run it.
Interestingly it should be compatible to all (or most) of the existing versions (HTC, BDS C, Small C..).