It's a reference to the GM streetcar conspiracy (most notably retold in Who Framed Roger Rabbit).

While it's a decently well-known anecdote, most experts nowadays believe that the very real attempt to monopolize the selling of buses to city transit did not contribute in any significant way to the dismantling of the streetcars--the streetcars were already in rude health and dying, and their rapid dismantling happened even in cities where the bus transit companies were not involved.