(a) Twentyeight million dollars ($28,000,000) shall be allocated to a joint powers agency responsible for expenditure for a rail project along the Santa Rosa to Larkspur rail corridor.
(b) Notwithstanding subdivision (a), eleven million dollars ($11,000,000) of the grant authorized by this section may be allocated to the Board of Supervisors of the County of Marin, and seventeen million dollars ($17,000,000) may be allocated to the Board of Supervisors of the County of Sonoma, for expenditure on the rail project described in subdivision (a) or for any of the purposes specified in Section 99628, if both boards concur.