A LONG time ago Dana Probert suggested a method to grab styles from one file and quickly add them to the current file (V1.0). Engineered Efficiency created a tool and placed it in their ProPack (V2.0). You can find the post here http://civil3drocks.blogspot.com/2006/07/super-secret-style-getter.html.
Civil 3D 2011 has two new tools. Read on…