I find this all very hard to understand. Citing a person who wants to sell you a metal bag to keep your phone in when you get up to no good certainly isn't helping.
If power is required, presumably the phone baseband has to wakes up and do something. A researcher could easily detect this by monitoring the power consumption or the local RF environment. Also baseband engineers and phone electronics manufacturers all have to have basically their entire design and engineering staff looped in to provide for this functionality. Where is this data?
If power is not required, nobody has yet presented any satisfactory explanation of how such passive tracking could even be possible over a wide area without being in very very close proximity to the device or having an unbelievably dense active sensor network. (NFC, silicon junction detection/fingerprinting, etc.) If this type of passive tracking is possible, then it certainly would not require that the device being tracked is even a phone.