Family Plot's subway sequence

I attended a seminar at which Ernest Lehman, the screenwriter of this film, indicated that he and Hitchcock indeed tried to get a subway sequence into "Family Plot." As the film was to be made in San Francisco and Los Angeles, the idea was to film in the then-new Bay Area Rapid Transit (BART) system in San Francisco.

Lehman said the scene was removed from the script mainly because it would cost too much, and replaced with the car scene.

I wonder: were Madame Blanche and George Lumley to get trapped in a speeding subway car or something?

Lehman also noted that the runaway car sequence was devised in some ways to "fix" problems that Lehman and Hitchcock always had with the "drunk drive" sequence in "North by Northwest." Key: removing all shots of the car hood from the POV angle, so that the road simply rushed directly into your eyes, with no hood in the way.