The speed is with "Due Prudence", no mention of of numbers in mph allowed over. The siren, again is to be used "Prudently" to avoid pedestrians and other vehicles and does not have to be sounding when the lights are on. Wig-wags are allowed by Fire Chief, if the Fire Chief is willing to do the paper work to turn one of his Volly's cars into a Class I Emergency Vehicle. This is not too likely to happen.
Stay safe and grow old!