City 17 is mod for Source Engine using Orange Box. He includes news weapons, new hud, news skins, e3_maps and more..
e3_bugbait is a official map from Valve in 2003 featuring a daytime Nova Prospekt. Remake of this map from City 17, a mod by Frere D'Arme unreleased in 2009.
So...what, do I install it in the same folder?
Install the map in 'maps' folder of your game (City 17 compatible)