It would seem that as ISPs implement DPI and protocol-specific traffic
shaping, they damage the arguments that they can make claiming they
have "common carrier" status with the inherent immunities that status
provides. I can hear the argument now: if an ISP can throttle
BitTorrent (or whatever) for specific nodes, why can't they also limit
the source addresses of packets coming from those nodes?
They can and should. I suspect many of them do as they
usually apply these filters to home networks.
BCP 38 is ~10 years old now. It should have been factored
into the purchasing decision of all the current equipement.
If it wasn't then the operator was negligent.