More exactly the Bluetooth is an AR3012 conected to USB but it is built into the WiFi module along the AR9462.
The AR3012 is a BT4.0 incl. low energy (aka “smart”) capable chip, based on a 32-bit CPU core by Tensilica which is again a MIPS derivate (AFAIK).
There is only little information available on the AR3012 and what this “firmware” is actually doing. There is a brief product flyer available e.g. here:
The binary firmware is available in the linux-firmware GIT:
AthrBT_0x11020100.dfu
ramps_0x11020100_40.dfu
which can be found here:
https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git/tree/ar3k
The Tensilica CPU cores are supported by the Gnu tools (GCC, binutils, gdb), maybe a round of disassembling might come up with something useful? Since the total binary code is ~50kb I doubt that this is the complete baseband. Using “strings” on the binaries already gives some insights.
Cheers
nicole