No that's a brush entity Stryker placed around the map. To get rid of that, you'll have to talk to Stryker.
What we are talking about are the models. Basically any model used in a map (called an env_model) isn't opaque. You can just walk right through as though it was just regular air. But now, they are opaque and you can't walk through them. The only way (previous to 1.2b) to make an env_model block a player was to have the mapper put in a 'Clip Brush' (an invisible block shaped like the model you are using) so that they would hit the invisible brush and be forced to go around.