By default the WebDAV connector is configured to access the collaboration areas of Nuxeo, which are at the moment the Workspace areas. This is the reason why no access has been given to sections through WebDAV.

SearchRootBackend contains the query defining this aspect:

SELECT * FROM Workspace WHERE ecm:mixinType <> 'HiddenInNavigation' AND  ecm:currentLifeCycleState <> 'deleted' AND ecm:isProxy = 0 ORDER BY ecm:path

To change this behavior you have to write an subclass with another query, create a factory equivalent to SearchBackendFactory to instantiate your class, and contribute this new factory through the backendFactory extension point.