Due to some RIB generation optimization in Renderman For Maya, the current frame value given to the Render Proxy is not correct when batch rendering a crowd simulation with motion blur (renders frame X-1 instead of frame X). More explanation can be find here.
To fix that issue, the Motion Blur type of Renderman For Maya must be set to Subframe instead of Frame. More information about Motion Blur Type in Renderman For Maya can be find here.
Motion Blur panel of the Renderman For Maya Render Settings