Pretty much. You'd need to use an IV calculator to compare the IVs of the Ditto and the offspring. I've always found Metalkid's one fairly handy.edit: oh wait. this is where an IV calculator would be essential i suppose. safe to assume genderless scouting is only possible with IV calculators then? i've never used one (new to the scene) but i'm sure it's intuitive enough.
edit: Thinking about it, once you know the IVs of the Ditto, you could plug them into the stat calculator on Metalkid's site and find out what the stats of a lvl 50 Magnemite with those IVs would be. That might be a bit more involved but you could then work out the inheritance directly from the in battle stats screen, as with Magikarps.