The move leaves Richard Rogers, Santiago Calatrava, Cesar Pelli and the regional office of SOM battling it out in the final round of the competition for a new skyscraper and transport hub for the Californian city.
The announcement comes just days after Norman Foster was beaten by Hawkins\Brown for the chance to design the prestigious redevelopment of Parliament Square, London. (AJ 15.03.07).
The winning practice in San Francisco will be expected to create a 21st-Century 'Grand Central of the West' - a reference to New York City's iconic Grand Central Station - housing eight transportation systems under one roof.
The elaborate project - estimated to cost $2-4 billion (£1-2 billion) - will incorporate an underground rail line running along the Embarcadero road, as well as bus and bullet-train connections to California's Central Valley.
There will also be a 150m tower on top of the building.
Approximately 16ha in size, the redevelopment will include nearly 3,400 new homes - 35 per cent of them affordable - 100,000m2 of office, hotel, and commercial space and 5,500m2 of retail space.
Meanwhile, Santiago Calatrava's Transbay California contest hopes have been overshadowed by public disquiet surrounding his proposed Chicago Spire development, which includes a 550m-tall twisting tribute to the city's founding fathers.
In a move to calm concerns over public amenities and traffic congestion, the prolific designer has stressed that the 1.3ha park will include many features suggested by worried locals, including areas for education, fishing and wetlands, pedestrian bridges and lakefront bike paths.
Some 150m higher than the Sears Tower - the tallest tower in the US - Calatrava's scheme will house 1,500 premium-priced apartments overlooking the heavily congested Streeterville neighbourhood.
Campaign group Streeterville Organisation of Active Residents (SOAR) will stage the first public meeting on the spire on March 26. SOAR president Gail Spreen told Chicago Tribune: 'We need more information on traffic.'