Womb Raider - S4-E21
Visible crew/equipment: While Piper, Phoebe, and Paige are in the magical cage, the Dark Priest, the demons, and the Seer are all killed/vanquished, then when Piper kicks open the cage the sisters walk out, and we can see the black mic transmitter attached to Phoebe's waist, at her back on the right. (00:38:40)
Answer: That was a mistake in the series.
Also, the episode is called 'Babies First Demon' and this alone tells us that it's Wyatt's first time in the field (so to speak) and as the sisters say, they've done a good job of clearing up their own magical messes so far. Nobody really knows how advanced Wyatt's powers are, or will become. That's why the cleaners appear, to nip things in the bud. The Cleaners didn't want to chance that the sisters could clean Wyatt's magic up, just incase they couldn't. Therefore intervening themselves, just in case.