The following is taken from the Halacha for Today email list (Ben Olam Haba):
Should a Shliach Tzibur make a bracha on shul Talis before davening Mincha?
The Mishna Berura (Siman Tallis to daven for the Amud he makes a Beracha. The reasoning is that the Shul tallis belongs to everyone, and thus it is "your" Tallis and requires a Bracha.) Paskens that when a Shatz puts on a Shul
However, the Biur Halacha (Dibur HaMaschil "Sh'Ala )brings a few opinios that perhaps one does not make a Beracha on a Shul Tallis, especially if he isn't wrapping himself in it/putting it over his head, as then it is only being done for kavod Hatzibbur and not for Mitzvah of Tzitzis, as well as some other reasons.
Rav Shlomo Zalmen Auerbach Zatzal (Halichos Shlomo Vol. 2 Perk 1 Ha'arah 2) says that the minhag is not to make a bracha on a shul Tallis. He says that even those that are machmir by Shachris and Mincha, still do not make a Bracha by Maariv.
Rav Yosef Shalom Elyashiv Zatzal says that it is best to have in mind when donning the Shul Tallis that you don't want to be "Zoche" in the Tallis, and then it won't be yours, and no Bracha is necessary.
The prevalent Minhag is indeed not to make a Bracha on a Shul Tallis, unless one is explicitly using it for the Mitzvah of tzitzis (such as one who forgot his tallis at home and is "borrowing" the Shuls Tallis)