I believe that there were two differing Qualcomm 7200 chipsets produced:
One with support for 850/900/1800/1900 MHz (the US version, in which the 850 & 1900 MHz band is used for UMTS). And one which supports 900/1800/1900/2100 MHz (for Europe) In which the 2100 MHz band is used for HSDPA.
You could be right though, it may be that the only differences are in software.
The device can't support all five frequencies(at least it shouldn't be able to :) ), but it may be possible to pick and choose by flashing radio roms.
Only time will tell... :)