Hello Mike,
The background on that car is surprisingly simple compared to some histories that old cars rack up. Wilde's '47 Cadillac limo was purchased new by the City of Milwaukee for use transporting visiting dignitaries. This is my assumption, but I'm assuming the red light was installed for use in police-lead processions. I believe the car wasn't officially retired until sometime in the 1970s, at which point it was purchased by a collector right away. It has since been passed around a couple different owners, but after its city career was finished, it entered the collector car community right away.
