Fedora 18 changes the way how to work with services in spec files. It introduces new macros - %systemd_post, %systemd_preun and %systemd_postun; which replace scriptlets from Fedora 17 and older (see https://fedoraproject.org/wiki/Packaging:ScriptletSnippets#Systemd, https://bugzilla.redhat.com/show_bug.cgi?id=850016).
The rbldnsd daemon needs configuration before it can run, and is designed to work with multiple differently-configured instances running simultaneously. Hence, the "preset" approach is not appropriate for use with rbldnsd. Any scripted installation scheme that could provide configuration for rbldnsd at install time could also enable rbldnsd, so I don't think any changes need to be made to rbldnsd for this.