And finally, check out the very detailed description of the Casio MT process described for the RZ-1:
Casio RZ-1 MT Jack - R-Massive
I didn't compare it completely with the CZ-5000 service manual, but my guess it's the same. At the end there seems to be a *.rar file with utilities--including MT Encoding and MT Decoding (according to the link/blurb).
It still might be easier to make a wav file, get it to someone, and have them play it realtime into a sequencer that will give you a standard midi file, but I was quite impressed to find this site and thought I'd pass it on to you in case you want to try it.
Uhoh. The suite of utilities might not be downloadable. :( It looks like it had been on a file sharing site called mediafire; not sure if that service is still around.