When you do have cooperative ISPs filtering DDoS traffic, it's usually a null route, so the IP under attack goes offline, but without taking the rest of the customers on your ISP offline.
He described system that would work the other way around, null-route the ATTACKERS, not the victim.
That's not quite how routing works -- null routing the attackers affects RETURN traffic to the attackers. By then, the damage is done, the target host is already overwhelmed with attack traffic.
Isn't that hard to do based on the distributed nature of DDOS attacks though?