Neither fish nor fowl
Neither a trolley nor railcar turned stationary diner, I stumbled upon something entirely different this AM while searching for prototypes of a model passenger car I'm considering adding to my roster.
According to their website, this year, the Newport & Narragansett (RI) Bay Railroad Company "extensively remodeled" their RDC 3 Buddliner #30 into a 1950's style diner (or soda fountain/ice cream shop depending on which web page you read). In addition to tables and chairs, this rolling "diner" has its own Wurlitzer jukebox.
A pre-renovation post on photo.nerail.org says that the 1950's car started as British Columbia Rail's BC-30. It was then sold to the Wilton (NH) Scenic, and then the Newport Dinner Train Islander. It is now "serving" as Conductor Kalbfus and the Ice Cream Train. Quite the mouthful. That's the scoop anyway (=supply groan here=).
photos.nerail.org Photo with history
1950's-style diner renovation (menu; see home page for photo of interior)
This Southern New England excursion company has a variety of nice looking offerings:
Newport & Narrgansett Railroad Website
Tomlinson Run Railroad