There are several sources, both academic and non-academic, that refer to the idea of a conspiracy, both pro and con:
Bianco, M. J. (1998). Kennedy, 60 Minutes and Roger Rabbit: Understanding conspiracy-theory explanations of the decline of urban mass transit (Discussion Paper 98-11). Portland, OR: University of Portland, Center for Urban Studies.
Cudahy, B. (1998). General Motors and mass transit...again. Transportation Quarterly, 52(1), 24-26.
El-Nasser, H. (2007, January 10). Cities rediscover allure of streetcars. USA Today. Retrieved July 20, 2009, from USA Today Web site:
http://www.usatoday.com/news/nation/2007-01-08-streetcars_x.htm.
Matus, P. (1974, September). Street railways: U.S. versus National City Lines recalled. The Third Rail. Retrieved December 30, 2006, from The Third Rail Web site:
http://thethirdrail.net/9905/agt1.htm.
Slater, C. (1997). General Motors and the demise of streetcars. Transportation Quarterly, 51(3), 45-66.
Snell, B. (2001, September 10). The streetcar conspiracy: General Motors deliberately destroyed public transit. Retrieved April 3, 2012, from LoveEarth Network Web site: www.lovearth.net/gmdeliberatelydestroyed.htm.
Zearfoss, C. (1998). Rebuttal to "GM and the demise of streetcars". Transportation Quarterly, 52(1), 15-23.
Two books on mass transit that I've enjoyed reading are Fischler (cited above) and Brian Cudahy, "Cash, Tokens and Transfers: a History of Mass Transit in North America". Fordham University Press, 1990.
Note that the Snell article is not the original 1974 report to Congress; that can be found at the end of Fischler's book. That article also refers to an earlier article, published in 1994 in the New Electric Railway Journal, which I have been unable to find online.
