As far as I know, all the current mobile phone operators go as high as 1.2 MBit?

Some NodeB's even in HSDPA networks still only have a single E1 transmission link. The NodeB would require four E1's and and that potential HSDPA bandwidth would be shared by the number of users on that base station. Speculatively it's possible that this bandwidth can be set lower or have vendor specific hardware bottlenecks in the equipment particularly if not upgraded to HSDPA (obviously)