Keep a sharp eye on that opposite side bearing!
Just kidding, the predictive power of a rear bearing failure for
opposite side failure is quite low.
Most important is that the failure mode of a wheel bearing is one of
the nicest of any part on a car. Almost never catastrophic ( unless
your ipod is always on high), they whine for a long time (usually weeks
to months even w/o lots of highway driving) before they die.
When faced with a whining rear end I would:
Remember that everything from the trans output brng to the road surface
is officially a suspect, since they all vary with road speed.
1 Check for a dry differential cause its easy and might save me thousands
2 Do the tire thing as you correctly did
3 In the absence of CV joints, dx the wheel bearings. I do not believe
the fault can be
correctly located by lateral loading (gentle curve or turn) since
everything between the wheels becomes loaded or unloaded with side
loads with no great consistentcy with regards to resulting noise
However the FACT THAT IT CHANGES WITH LATERAL LOADS DOES help eliminate
tyres as the cause.
Tires are suggested by a noise that varies with different road surfaces
in a fashion that one can make sense of.
Lastly hard machanical noises will increase in pitch and volume pretty
much with road speed.
Tire noise will more often show a non-linear noise with a "band" of
noise say between 55 and low 70s mph the noise peaks, because it is a
complicated harmonic of air flow. No one is able to design a tire that
is quiet new and quiet thru all of its tread depth
Sorry for the long post, best of luck.