I would think that if elephants are smart enough to learn that recorded buzzing is not a threat then they will also learn that the fake hives don't pose a threat.
Apparently, they did use recordings and it did have effect on the elephants in Sri Lanka.
> we used a recording of a disturbed hive of cavity-dwelling Asian honey bees (Apis cerana indica) and conducted sound playbacks to 120 wild elephants in 28 different groups resting under trees in Uda Walawe National Park in Sri Lanka. Elephants responded by moving significantly further away from their resting site in bee playback trials compared to controls. Elephants also increased vocalization rates, as well as investigative and reassurance behaviours in response to bee sounds, but did not display dusting or headshaking behaviour
It worked in the short term since elephants weren't expecting to be fooled. But it is possible that if they hear the sound of buzzing enough times without seeing any bees, they will start to disregard it.
Fear of bees is clearly a learned behavior in elephants.
