For anyone interested, I found this article: http://autos.aol.com/cars-Toyota-Hig.../expert-review

It includes this particular paragraph about rear wheel power:

"The all-wheel-drive system in the gas models provides a full-time 50/50 front/rear torque split. In Hybrid models, the AWD system is front-drive biased, but when it detects slippage, the rear-mounted electric motor can kick in to deliver up to 25 percent of the available power to the rear wheels. Both systems will help you get the kids to school on snowy days."