as long as you have proper quantities of what are considered the 'essential' amino acids you can build muscle optimally, you can still build muscle off incomplete proteins, but your body is going to have to break down other tissues to get the amino acids required, so it's a slower process. some beans may be lacking in quantity of 1, 2 or more amino acids, however I imagine those 'bean medley's' would probably be good.
What I use to do is I'd get some bean medley crush it up and put it in a pita, now that's complete protein for sure.
any time you mix some legume and grain source of protein it's most likely going to give you enough of the essential amino acids to be useful, IT ALL BREAKS DOWN TO AMOUNT OF THE PROPER AMINO ACIDS AVAILABLE, IT REALLY DOESN'T MATTER WHERE YOU GET THE FROM!!!
PEOPLE WHO SAY YOU HAVE TO SLAM DOWN STEAKS TO PACK ON MUSCLE ARE FUCKING LIARS! AND THEY NEED TO LOOSE SOME WEIGHT!