Well, the whole thing was broadcast "live and uninterrupted" on the VOA Shortwave Service, so they could have been listening to that.
But that would probably have included the Quindar tones, and we didn't hear them. Also, the relative timings of the Capcom and Apollo astronauts would match the recordings made at Houston and available on the AFJ and ALSJ. They don't.
The Quindar tones were used to mute and unmute the uplink transmitter. Because a long series of analog phone lines connected Houston to the uplink station, background noise on those lines would ordinarily be continuously transmitted to the astronauts. The Quindar tones, generated at Houston, activated and deactivated a muting relay at the uplink transmitter so that any phone line noise would be transmitted only when a Capcom was actually talking.
The Quindar tones were removed at the uplink station with a pair of narrow audio notch filters (note the key and unkey tones have slightly different pitches). So the beeps that made NASA so distinctive were, ironically, not heard by the astronauts.
The fact that we didn't hear the Quindar tones in the Jodrell Bank recordings strongly suggests we were hearing the actual uplink transmission. The short pause between one of McCandless's comments and Apollo's reply pretty much confirms we were hearing the uplink via the moon. It certainly should have worked; the uplink was a very powerful signal, and enough would have reflected off the moon to be audible at such a large dish.