I went to a factory auction 30 years ago in eastern Mass where they made porcelain signs. Probably one of the last in the country. They had a huge oven that had to run 24/7. They couldn't shut it down because it took too long to get it to operating temperature. It looks like the Bangor and Aroostock RR chose to use a cheaper alternaive.
There is a guy on eBay who will make vinyl on aluminum signs. I have a standing search using my name "Wardner". Several times a year, eBay will send me an alert for a town sign lettered "Wardner, ID)". The signs are less than $20. The town was named after my great grandfather around 1890.