The M"B paskens in 14:11 that if a person takes a shul talis to get an aliya or daven for the amud he is obligated to say a bracha on the talis. The logic here is that the shul talis is jointly owned by everyone in the shul. Therefore, just like you would say a bracha on your own talis, you should say a bracha on the shul talis.
Maybe I am wrong, but my impression is that most people do not recite a bracha when they take a shul talis to daven for the amud. Maybe the reason why is because if you fast forward to the M"B in 18:5, there he paskens that anyone who davens for the amud, even someone who says kadish, needs to put on a talis; however, since he is just wearing the talis for kavod tzibur and not as a garment, no bracha is recited.
I am not sure how you get these two M"B's to fit together. In 14:11 M"B applies the sevara of the garment being worn only l'kavod tzibur only to a talis borrowed from another individual. It sounds like the concern is that since you are borrowing the talis only for the purpose of kavod tzibur, the person lending it is not really makneh it to you for use as a garment. However, if the talis belongs to you, or is the shul talis, i.e. it belongs to everyone, then even if you put it purely l'kavod tzibur, a bracha is required. Yet this seems to fly in the face of the psak in 18:5.