Yes they do. A Faraday cage is equally good at blocking radio waves going out as coming in. They don't protect against conducted emissions though - along a power cable for example - so they're not a complete solution.
Perhaps the radiation wasn't mostly coming from the Antminer box itself - each 700Mhz clock the rig draws current, the transformer propagates it back to the wall, and the power lines in the flat become a big antenna.
Powerline Ethernet has this problem, but it uses only a 25MHz carrier wave, so it only bothers hams.
Powerline Ethernet has this problem, but it uses only a 25MHz carrier wave, so it only bothers hams.