All right, I just got Lucario from Korinna. I know it's set to have 31 IVs in Speed, but are the rest of the IVs set, or randomly determined like any other Pokemon?
HP: 4-6 Attack: 24-26 Defense: 14-16 Sp. Atk: 24-26 Sp. Def: 17-19 Speed: 30-31
The IVs are fixed every time. So you cannot soft-reset. Sorry.
Hope I helped. :) Source