Well, I just spoke to the service manager at my dealership yesterday, cause I thought I had the "new" brake pads on order. It turns out they are just the pads to fix the squeaking while cold TSB, which my car is already equipped with (build 02/04). He said that while they have had a couple complaints about grooving and grinding on the rear rotors, there was no fix for it yet. He called Mazda Canada on my insistence and called me back, but no luck. Mazda Canada said there is no fix in the works at this time. He told me to hang on for now as having my pads replaced under warranty would just net me a new set of the pads I've already got and some machined rotors.
This sucks especially since the parts counter chick told me she had ordered the "new" pads to fix this problem, turns out they were just the pads I already have. For now all I can suggest is everyone contact their dealer and have them call Mazda Canada or USA and report the customers concern. Perhaps if we have enough dealers calling they'll feel pressured to address the problem. Of course this only works if enough people actually take action.