did the working class ever hold political power in Bolshevist Russia?
No, of course not. Bolshevist Russia differs from Tsarist Russia only in that it was at least theoretically possible to rise out of the ranks of the Dispossessed, not in the power held by the Dispossessed.
Oh, you mean during the Civil War? Well, the working classes had the power that being on the right side of a gun gives you - the power to settle some very old scores. Most of the Red Army commanders were workingmen.
As to the Soviets... nobody really held power during 1917. It was more like a power vacuum.