What I don't get about this is how the new system is discovered in the first place, assuming the attacker is not already on the network. Sure, gain fast access, but why would you let the traffic on to the local net to discover the machine (except for examples). I can see a box stuck on a home connection getting pwned quick, but surely a Uni network would be blocking rdp traffic, or external pings, or whatever it was that was being used to find and pwn XP computers so quickly??

Wouldn't multiple attackers have to be effectively flooding the network with pings or service/port access attempts to find a new computer so fast?

At that time? At a university? No. You typically got a public IP address via DHCP and there was no firewall at all. Even today that's still pretty much the case, though a new device is probably assigned a non-routable address until a terms of use agreement is clicked.

They were talking about a XP facing the internet, so without network protections like blocking pings.