I seem to recall the drums that they sell drums that are cryogenically cooled, but I don't really see how you can affect the structure of something that is so far into it's solid phase as room temperature iron. Perhaps Big Dave's engineering background can enlighten us.
Cryogenic cooling shrinks the grains in the metal making it stronger (great for an axle or a transmission input shaft), but I can not see any real advantage to extending wear in terms of a brake drum. To make a better drum they should cast them out of steel not grey cast iron. That way you could weld the interior of the drum with Chromium, Molybdenum, Manganese or Vanadium to change the hardness and wear characteristics of a drum. But then again if they ever did this no one would ever buy another brake drum as the old ones could be rebuilt rather than turned into Isuzus or Kias.
Cryo treatment greatly enhances the wear capabilty of steel. Its used in Formula One and the high tech racing levels but these guys try to keep their "improvements" to themselves.
Also used a lot in the firearm industry to reduce barrel wear...
If you swap the entire backing plate and brake assembly over you could make it happen but just using those drums won't work I don't think.But FWIW try it, what the hell ? it might work.
BUT for the trouble it may cause you'd probably be better off with converting to disc brakes.