AFAIK Market St. was always standard gauge(save for that mutant duorail in the lower depths). Both the cable cars and post 1906 the streetcars. It would appear the earlier horsecars on Market were also standard gauge since the last horsecar to operate in 1913 came off Sutter onto lower Market.
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www.cable-car-guy.com]
Still don't know exactly how the Sacramento St. cable cars got onto the line from Washington & Mason carhouse. Cable lines emanating from Washington & Mason and California & Hyde carhouses were all 42" gauge.