Well, I've managed to get the keyboard working over USB, sort of... I followed Soarer's modification page, but not having a spare processor socket, I soldered the Teensy directly to the PCB using pins and wiring.
Then I bashed my way through loading Soarer's Converter code, and after much trial and error managed to load the 6112884.sc configuration file created for this keyboard. It does work, after a fashion; i.e., pressing most keys returns some result. Just not the one the key is labeled with.
Not sure if my wiring is at fault, bad solder job, or if I missed a step in the code. I'll try to troubleshoot the issues tomorrow, my error rate gets pretty high the later I try to work.