Goodrich ISR sensor equipment has been able to do this for a while regardless of the type of plastic for the purpose of quality control in product containers:
http://www.sensorsinc.com/image_powderswirenlarge.html ... "While a visible camera cannot see through plastics, these same plastics are transparent with the short wave infrared. Goodrich ISR-P cameras can see through plastic to detect the fill level of a product. This capability is extremely helpful in quality control and process control applications."
http://www.sensorsinc.com/image_powderswirenlarge.html ... "While a visible camera cannot see through plastics, these same plastics are transparent with the short wave infrared. Goodrich ISR-P cameras can see through plastic to detect the fill level of a product. This capability is extremely helpful in quality control and process control applications."