F12 installed by default the openfwwf driver and firmwares for broadcom wifi cards (See on their site the ones running with it: http://www.ing.unibs.it/openfwwf/
); but f12 uses a non-free kernel; So the firmware is installed in /lib/firmware/b43/ and the linux-libre doesn't load it. You have to create a new file: /lib/firmware/b43-open/ and copy the firmwares in it.
You can do as this:
#cp /lib/firmware/b43/*.fw /lib/firmware/b43-open/
And it'd work
We have to modify openfwwf package for it to install the firmwares in /lib/firmware/b43-open/ and not in the b43 file.