I think this thread is now sufficiently circular that it can be consigned to a file of a similar shape.
However, I'll pop in to say clarify the distinction between "intercept" and Subscriber Traffic Management; one is opening the envelope and then deciding what to do with it, the other is delivering only 100 kilograms of post a day. That's it. Is the latter fair? Different question.
Everything I have read indicates that STM is applied at the link layer; it treats packets as nothing more than collections of bits, agnostic of their content, their port, their routing, the application that produced them. If you have a look at this precis of a
training course for lawful intercept you'll see that while it does mention Cisco protocols, it doesn't mention the STM architecture at all. This is because intercept and traffic management are two different things. As an ISP Virgin Media will have various processes for complying with requests from legal authorities, and if my understanding is correct they operate at the Head-End rather than at the UBR/CMTS. Standard practise is literal mirroring, splitting the optical stream and discarding packets not routed to the subject of the inquiry. The reason that this mechanism is used is that it is effectively lossless, and creates no perceptible delay. Use of this sort of technology is pretty firmly governed already, by RIPA and parts of law like it. I delve into intercept technology only to illustrate that it's not the same as traffic management. It takes place at a different layer of the network; it uses different equipment; it interacts with packets for their content rather than for their weight; it is qualitatively different.
That doesn't speak to the fairness of implementing it to alleviate network load caused in part by a lack of foresight and a mixture of avarice, haplessness, and gormlessness, nor to the legality of variation in Terms & Conditions that form part of a contract, but to suggest that STM is
illegal because it constitutes 'intercept' is to find oneself barking, if you will, up the wrong tree.
Of course, what I say doesn't matter. It's an "open secret" that Richard Branson is looking at your naked photos, and that there's a dial in every former NTL and Telewest cabinet that can be adjusted between "upset" and "satisfy". Wilson actually won election by lining the pockets of the BT engineers who used to adjust similar components in telephone exchanges. Thatcher's knife-fight cable market free for all was reward for their treason.