CAN bus messages from BMS?

I don’t know of a published source for the on-the-wire formats of digital messages used in Toyota vehicles. Such information generally isn’t needed for maintenance or repair, so there’s no reason to disclose this intellectual property.

Your question seems to contain some assumptions that may not be correct, by the way. On Prius Plug-in cars, battery management is a function of the power management control ECU, the computer that also runs the hybrid system. As New Car Features (more info) explains, there is a separate battery smart unit, which “converts the HV battery related signals (voltage, current and temperature) into digital signals, and transmits them to the power management control ECU via serial communication,” but the state-of-charge calculation is done by the power management control ECU.

The serial communication with the battery smart unit isn’t described as CAN or mentioned in the Repair Manual coverage of the CAN communication system. See also this older PriusChat thread; it was about third-generation Prius cars, but the illustration of the serial waveforms looks the same as the one in the Prius Plug-in manuals.