Wow, I wouldn't necessarily try doing a firmware upgrade of your own. If you encounter problems, going back to the original firmware could be difficult (Apple may well have modified it for their devices, they don't make it available, etc).
I'm not sure if Apple used a CSR chip or not - could also be Broadcom. Apple hasn't released the full technical specifications book on the MacBook yet, but you could find out yourself by opening up your MacBook and checking. The disassembly guide is on iFixit, here's the part where the Bluetooth chipset is removed:
http://www.ifixit.com/Guide/85.1.7.html
Note that this procedure may invalidate your warranty, but if you're considering flashing the firmware yourself, that's probably not an issue for you.
