Only answer if:
- you have tested this yourself or seen it work.
- can provide a link to strong evidence that it will work.
Please no "should work" answers, I know it should work.
Let me answer my own question. YES the PowerMac G5 supports 2TB drives. I installed 2x2TB Western Digital drives in my PowerMac G5 Dual 1.8 Ghz in a RAID-1 configuration.