MIMO antennas aren't transmitting in your direction unless you get their attention by transmitting in theirs. Also, they might be transmitting by default with b

MIMO antennas aren't transmitting in your direction unless you get their attention by transmitting in theirs. Also, they might be transmitting by default with barely-enough power, in a narrow band, in frequencies everyone generally agrees to not use for anything important; but once you establish a circuit with them, they could start transmitting in your particular direction with more power, in wider bandwidth, or in more-likely-to-be-reserved frequencies.