A similar plan to run diesel multiple unit trains across Altamont Pass was proposed by BART in 2003, though it comprised a larger service area (continuing north along the Iron Horse Regional Trail, a former Southern Pacific right-of-way).

[15] The final environmental impact report was approved by the board in May 2021, allowing the rail authority to proceed with design and continue seeking funding for the project.

[16] By 2023, the locally preferred alternative had the line utilizing the I-580 median and Western Pacific alignment until realigning with I-580 north of the Summit Tunnel and continuing east to Mountain House.

[17] Selection of the alternate Mountain House station location and alignment east of Altamont Pass forced the agency to redo part of the EIR.

[19] Valley Link is a plan to utilize zero-emission hydrogen trainsets[3][4][5] along the former first transcontinental railroad right-of-way through the Altamont Pass and in the Interstate 580 median through the city of Livermore.

[21] The developer of River Islands has offered to cover the cost of station construction in exchange for the ability to build a transit village at the site.

[22] In 2018, Stadler met with the governing board to discuss traction sources; diesel multiple unit or diesel/battery electric hybrid vehicles will likely serve the route.

[8] Funding for the feasibility study was provided variously by Caltrans, Metropolitan Transportation Commission, and the San Joaquin County Council of Governments.