The power savings estimation for low power mode would be around 0.19Watts to 0.45Watts, depending on different mode and core frequency, based on nominal process distribution, and the total savings would be N times the number of used cores
There is detail core power dissipation data and low power mode saving estimation data in T1042_T1022 Hardware Specifications RevG.pdf, in Table 10. Single core, Single cluster low power mode power savings, 1.0V. You can contact Freescale to get this doc.