Import or create your model as an Object3D.
Set the Object3D's collision mode to COLLISION_CHECK_OTHERS.
Now when you want to move the camera in direction 'dir' by 'dist' units, first use;
yourWorld.calcMinDistance(cameraPos, dir, dist)
if this returns Object3D.COLLISION_NONE there'd be no collision, otherwise the camera would hit the model 'dist' units along vector 'dir'...