I offer some perspective on how DMCA Safe Harbor is used outside of the ISP realm.
The organization that I work for maintains DMCA Safe Harbor status. We are a legal technology service provider, which in English means that we collect data involved in litigation and process it so that it can be entered into evidence as part of a legal proceeding. We have Safe Harbor protection in case we happen to collect copyrighted media during the course of doing forensics collections on systems that we do not own. In order to maintain our status, we have to take reasonable measures to ensure that we are not facilitating copyright infringement. What that means in practice is the security team monitors the network to make sure that people are not running bitTorrent, hosting FTP sites or otherwise actively sharing copyrighted content.
We have never once been served with a take down notice or had to remove content from our systems.
Regarding the article and the DMCA, it seems to me that all Cox has to do is provide subscriber information. It is up to the content holders to go after the individual infringers and make them remove the content from their systems, one lawsuit at a time. Cox and the ISPs are simply providing transit services. They are not actually hosting the content and do not own the systems hosting the content. While I applaud Cox for trying to shield their customers from frivolous lawsuits, I think they are being stupid here. We all know that the large majority of bitTorrent traffic is piracy. If the pirates are too cheap / stupid to spend $10 a month on a VPN or proxy service to obfuscate their connections, they deserve to go down.