Assuming the motor is from a Federal Q siren I seriously doubt it has any value as a ebike motor. I remember the first time I used one, it was in a 1942 Seagrave V12 fire engine with dual everything from spark plugs to generators and when you pressed the siren button the headlights would dim!
Years later I had a 1970 Pontiac ambulance equipped with one. This unit had about a 460 cubic inch engine and a 165 amp alternator and when the siren was blown the lights would dim.
By the early '80's when I could afford to buy new ambulance the days of the Federal Q were, thankfully, history and the age of electronic sirens was in. They were louder and while they still drew a lot of power they did not even touch the Q for draw. When I sold out almost 13 years ago there were still a few old Federal Q's in the parts room, I couldn't even give them away.
Things have changed of course, I recently attended a antique auto meet and a fellow had a '70 Pontiac US Air Force ambulance with a Q and he valued it at over 20K. I junked half a dozen of them simply to get the parking spaces twenty years ago.
I believe you cannot get enough batteries on a bicycle to power it. But, it may not take as much juice to run a bike as it did to make noise as it made a LOT of noise.
Mike