"Nosey Smurf is the 'hot mic' tool. For example if it's in your pocket, [GCHQ] can turn the microphone on and listen to everything that's going on around you - even if your phone is switched off because they've got the other tools for turning it on."

Are they implying that all/most smartphones still communicate with cell towers when turned off? (obviously this isnt happening) - Or do they pwn the device before hand to have it fake that its turning off while remaining on?