Originally posted by JohnX AFAIK it's the number and shape of the aperture blades that largely determine the bokeh, not so much the max. aperture.
This is quite incorrect. Background Bokeh is largely determined by optical formula of the lens itself. Some lenses are over-corrected for aberration and might not have as smooth of a bokeh, while under-corrected would have smoother bokeh with the usual less sharpness. Of course, the inherent DOF is determined by aperture, while the number and shape of blades only dictates the shape of point light. That is not at all important since the shot was taken at near WO (f/1.6).
Back to the OP, you can definitely get similar look with the 55/1.4. However, ISO would play its part in the picture as well. To full body like that with a shallower DOF, you can take 4 or more pictures and stitch them together (I forgot the name of the technique). Of course, it has to be done with practice. But don't go too wild with shallow DOF. This picture would be less interesting if the DOF is thinner.