Using SVN trunk, this now works:
sudo sa-update && sudo /etc/init.d/spamassassin reload
note that you need to import the GPG key:
wget http://spamassassin.apache.org/updates/GPG.KEY
gpg --import GPG.KEY
The updates are being distributed via Coral (http://coralcdn.org/) to save
load. They are generated nightly based on "rules/active.list", which is
generated based on freqs from the previous day's mass-checks, and sandbox
rules will be published via updates if they pass the publishing criteria
-- all as per recent discussions on this list.
So if you've got good, fresh rules, it might be worth throwing them
into a sandbox now, and see if they get published ;)
--j.