Ok.. so it's not really missing, just not in the wiki. My appologies
For anyone who needs the command, here it is: MLElkM1|ZV~<<zonenumber>> (Thanks Dave!)
This will give the ANALOG voltage on that zone. What I haven't figured out is where the A/D converted value is -- that is the 8-bit integer 0-255. It is accessible via the ELK keypad and nowhere else that I can find which makes the whole A/D converter useless.