Hmm, lot's of misconceptions going on here, so as a as head of technical liason for a major TV manufacturer, an ex-principal BBC technical engineer and an advisor to TV licencing, perhaps I'll chuck my four pennyworth in.
TV detection is not smoke and mirrors. They have always been able to detect the reception of TV programs. For many years, TV detection was limited by the proximity of the detector van to the receiving equipment. This is no longer the case. Specialist hand held devices are available which can be taken up the stairs in blocks of flats etc and can indeed not only detect reception but a whole swathe of other information as well (NB. This is not confined to the channel being watched but other things as well!)
TV detector vans do not require ip adddress from isp's. The question of cost is immaterial OG. The principle is what matters here not the cost and millions are invested in the technology where the return is a mere fraction. That doesn't matter a jot as evasion is regarded as a prosecutable offence.
Packet Detection technology is indeed used but there is far more to it than has been published in the press. Licensed Radio Ham's can tell you a great deal about this technology should you desire to know more. However, it's not all about Packet Detection by a long chalk.
Jackthehat, it's untrue that there have been no successful prosecutions for detection by detector vans. If you take the contrary view, please cite the evidence.
Your television equipment both receives and transmits detectable signals and any view to the contrary is simply wrong.
Rest assured, I'm thoroughly familiar with the equipment used including the current state-of-the-art devices. Packet reception merely allows them to do their job more rapidly than previously. I can also confirm that the authorities have for some time been able to access and use router information.