I found this old video of a late-1940's ephemeral film produced by AT&T about old-fashioned mobile telephones called (what else?) "Mobile Telephones."

https://www.youtube.com/watch?v=xDy2tHCPdk8&list=WL&index=96

Pre-1950 cars, trucks and buses are all over this one. Maybe somebody could add this video. Or maybe I can, once I find an exact year and other details.