/usr/include/OGRE/Plugins/BSPSceneManager/ is in libogre-1.9-dev 1.9.0+dfsg1-7.
This file is owned by root:root, with mode 0o755.
..
/usr/include/OGRE/Plugins/BSPSceneManager/OgreBspLevel.h
/usr/include/OGRE/Plugins/BSPSceneManager/OgreBspNode.h
/usr/include/OGRE/Plugins/BSPSceneManager/OgreBspPrerequisites.h
/usr/include/OGRE/Plugins/BSPSceneManager/OgreBspResourceManager.h
/usr/include/OGRE/Plugins/BSPSceneManager/OgreBspSceneManager.h
/usr/include/OGRE/Plugins/BSPSceneManager/OgreBspSceneManagerPlugin.h
/usr/include/OGRE/Plugins/BSPSceneManager/OgreBspSceneNode.h
/usr/include/OGRE/Plugins/BSPSceneManager/OgreQuake3Level.h
/usr/include/OGRE/Plugins/BSPSceneManager/OgreQuake3Shader.h
/usr/include/OGRE/Plugins/BSPSceneManager/OgreQuake3ShaderManager.h
/usr/include/OGRE/Plugins/BSPSceneManager/OgreQuake3Types.h