Wild contraption on the Southern Pacific of Mexico:

http://abpr.railfan.net/abprphoto.cgi?m ... anColl.jpg

The bus came from Greyhound Pacific within which SP had an ownership interest. Before that I think the bus was used by Pickwick Stages, a Greyhound predecessor.

There were also former Pacific Electric buses converted to rail for the operation in Mexico. Included were some open-top double-deck buses that once ran down Wilshire Blvd in Los Angeles.