YES ! Here it is...
Pick an unused local facility ie local5.
Configure SA log to that facility by using the -s parameter.
spamd -s local5
Configure your syslogd to dump local5.* into a separate file, and exclude it from your other logs. Here's a quick syslog.conf example:
*.info;mail.none;authpriv.none;cron.none;local5.none; /var/log/messages
local5.*; /var/log/spamassassin