At one stage, some people on comp.sys.sinclair discovered some .itm and .pan files, which apparently come from a piece of software called Intermega running on MSXs.
I got my hands on a few of these, and after a bit of hacking around, I've worked the format out, so here is itm2tap, a very simple program to convert .itm and .pan files into .tap tape images, as used by many Spectrum emulators.
The DOS executable will require a DPMI server to run; see here for details.
The format of these files, as far as I can work out, is detailed in the comp.sys.sinclair FAQ.