We changed slightly the behaviour to include the new "Look-At" mode:
a) The Billboard items (Geometry->Template) look at the active camera automatically, if Camera->Look-At->On is enabled.
b) For standard objects (Geometry->Custom Object) it is necessary to assign the target (that may be a camera or something else) to Camera->Look-At->Target and enable the "On" checkbox.
This allow to use a separate target for the Look-At feature, while using the Camera clipping.