Theoretically anyway. CYP3A4 is responsible for the N -demethylation process that produces the less active metabolites(Norcodeine from Codeine, Norhydrocodone from Hydrocodone, Noroxycodone from Oxycodone, etc.) while CYP2D6 is responsible for the O -demethylation, which creates the much more active metabolites(Morphine from Codeine, Hydromorphone from Hydrocodone, and Oxymorphone from Oxycodone).
As to how well it actually works, though, I don't think anyone can say for sure. I've never personally noticed a big difference between taking Opioids with grapefruit juice and without. I'd imagine the difference would be much more apparent to someone who's never taken Opiates before.