There is no mention of the read broadcast being overlaid by or fading into the attackers signal, which I would expect if they were pointing an antenna very carefully to maximize their attack.
Instead, I think someone physically unplugged a signal cable somewhere and plugged in their own feed. Possibly even an insider.
-Just wagering a guess here - the link was probably frequency modulated; an FM receiver has a very strong capture effect - the strongest signal received on the tuned frequency is the only one demodulated; any other, weaker signals are effectively just raising the noise floor.
Instead, I think someone physically unplugged a signal cable somewhere and plugged in their own feed. Possibly even an insider.