Lion Server - Spamassassin Shortciruit Plugin - Is it enabled by default?

The config file for spamassassin in Lion (/etc/mail/spamassassin/local.cf) contains entries for configuring the shortcircuit plugin (e.g. for whitelisting sites etc.)

ifplugin Mail::SpamAssassin::Plugin::Shortcircuit
#
#   default: strongly-whitelisted mails are *really* whitelisted now, if the
#   shortcircuiting plugin is active, causing early exit to save CPU load.
#   Uncomment to turn this on
#
# shortcircuit USER_IN_WHITELIST       on
# shortcircuit USER_IN_DEF_WHITELIST   on
# shortcircuit USER_IN_ALL_SPAM_TO     on
# shortcircuit SUBJECT_IN_WHITELIST    on


#   the opposite; blacklisted mails can also save CPU
#
# shortcircuit USER_IN_BLACKLIST       on
# shortcircuit USER_IN_BLACKLIST_TO    on
# shortcircuit SUBJECT_IN_BLACKLIST    on


#   if you have taken the time to correctly specify your "trusted_networks",
#   this is another good way to save CPU
#
# shortcircuit ALL_TRUSTED             on


#   and a well-trained bayes DB can save running rules, too
#
# shortcircuit BAYES_99                spam
# shortcircuit BAYES_00                ham


endif # Mail::SpamAssassin::Plugin::Shortcircuit

Is this plugin installed for Lion and is it enabled? If not, how do I install / enable?

Thanks in advance.