HC, not the most helpful of answers!
However, from what I can see, signal averaging does exactly what we want - it identifies and amplifies vibrations that might otherwise be masked and lost in the 'noise' from correctly functioning parts of the gearbox. If they can do it with the human heart then a MRGB shouldn't be that tricky.
Since a MRGB will have a reasonably consistent 'signature' in the cruise (where most spend the majority of their time), anything that suddenly, or even gradually diverges from that norm should be questioned as it may be the portent of a failure.
Perhaps if you have more detailed information you might like to share it instead of being so dismissive.