John,
Working for a governmental ISP, the fact is that traffic, regardless if it's noise or legitimate (which can only be determined by Deep Packet Inspection), can only be stopped at the border. Once stopped at the border, you still have incurred the inbound bandwidth costs.
Those running IPENCAP tunnels deal with this today, traffic destined to our subnets still reaches our gateways, and the bandwidth has been spent. This is regardless of a firewall to prevent traffic from entering the subnet, or a Destination Unreachable returned. That cannot be changed, as 44/8 are public IP addresses. Traffic must be at your border, that's the point of routing.
-KB3VWG