I follow DP Shane Hurlbut A.S.C on his Inner Circle and he frequently discusses shooting with multiple cameras.
He has a film coming out next year where the director regularly wanted three camera coverage. The typical set up was all cameras on Movi gimbal set up as Cam 1) a two shot wide and Cam 2 & 3) Over the shoulder.
For most of these set ups, it looked like one to two boom ops would be able to cover with good coverage by booming from the same side as the wide camera.
So whether its one camera out multiples, I think with a good director of photography it's possible to cover with the usual number of boom ops. And as always good communication! Which is hard if the other departments don't properly value the sound department and set them up for success.