San Francisco Bay Area, California
BART Permits for Film, Video and Photos states: WHEN A PERMIT IS NOT REQUIRED: BART is a Bay Area icon. As such, it attracts more than a few amateur photographers. If you are a paying passenger making your way from point A to point B, then there is no specific prohibition to taking photographs in areas that are accessible to the public provided you do not appear to be a security threat, involved in a commercial activity or harassing other riders. If, however, you appear to be taking photographs of potentially sensitive areas or obviously involved in some commercial enterprise like an advertising agency, BART employees, especially BART Police Officers, may approach you and ask you to identify yourself and possibly take further action against you.
SF MUNI Photography and Videography Guidelines states: Non-commercial Photography and Videography. The general public is permitted to use personal, handheld photography and videography equipment on all Muni in-service transit vehicles and on publicly-accessible SFMTA property, including Muni stations, as long as such activities do not interfere with transit operations.
Bay Area Rapid Transit (BART). The official site of the BART system.
San Francisco MUNI. Official site of the San Francisco transit operator.
Market Street Railway. Official site of the organization which has restored the PCC streetcars to Market Street.
San Francisco Cable Car Museum. Official site of the Cable Car Museum. Includes photos, history, museum information, and "anatomy of how a cable car operates."
MUNI Central Control. A Java applet showing locations of trains in the Muni Metro subway.
San Francisco Cable Cars. An unofficial site dedicated to San Francisco's cable cars-- history, operations, and practical information.
San Francisco Market Street Railway Operations. A page of history regarding the (original) Market Street Railway System's operations, from the S.F. Museum.