Turns out the list is hosted at IBM’s SoftLayer business, which is known to be excessively spammy. See Krebs’ article, “IBM Runs World’s Worst Spam-Hosting ISP?”
SoftLayer’s reputation here isn’t theoretical. This campus blocks over 300,000+ spam messages daily from SoftLayer. A particular spammer gets a new VPS and network range each day, then spams for a while. As I type this we’ve blocked over 56,000 today from a new /16. Due to this real-world impact, our administrators recently blocked all of SoftLayer.
Thus, we can no longer receive postings from the bigmail.bigfix.com mailing lists.
(They put in an exception for me. But IBM has a self-created problem here.)