The radio is hardware in the phone and does not change based on the ROM you load. So, to answer your question, no, CM7 does not use any different radio than the stock OS load.
Also, Blur is just a launcher, not the OS and Blur has nothing to do with the radio.
Now, if CM7 uses any different Drivers for the radio, I don't know. However, there are not that many drivers out there for the hardware and the CM team tends to stick with the stock drivers as released by the OEM's in their SDK's. Focusing more on the interface and user experience of the ROM than re-inventing the wheel.