Tunnel arbitrage shared funding of BART Muni rail

In the beginning when the Voters Approved the BART system the city of San Francisco was gifted with the MUNI system sharing stations along Market street.BART’s gift was the tunneling costs.The time might be to consider again sharing tunneling costs to encourage an early deployment of a Second BART tube.Both MUNI and BART have studied a Geary street tunnel and it is this that speaks for a joint tunnel study.The systems would not share tracks of course but would share tunnel costs of a two level tunnel.What to study?

(A)(1) BART and MUNI share a two level tunnel out to ocean beach and share stations but in most cases BART trains would expressed by many stations without stopping.Software shared by both BART and MUNI could monitor this and alter the stops made by both MUNI and BART to accommodate traffic levels on both in real time.

(A)(2) BART or MUNI does not run all the way out to Ocean Beach and shared two level tunnel ends.Or two level tunnel continues a way South  but this would require a MUNI Geary tunnel sharing a tunnel with another MUNI line heading south.However BART out to Ocean Beach could allow MUNI to run trains through Geary tunnel that serve two different lines but not likely during busy periods.

(A)(3) No recent BART or MUNI studies discuss using the Bay Bridge instead of a tunnel.High speed rail tunnel sharing with BART or MUNI has not been studied although I have discussed it in earlier posts regarding sharing a two level tunnel under San Jose.

Questions?

(B)(1) A two level tunnel like Market street MUNI/BART would cost more to dig(?) Shared stations would as well so there must be a financing / ridership synergy.Ridership synergies are elusive but financing tunnels between agencies I think might be the opportunity we seek.Agencies could owe one another for costs and capitalized over time; example agency 1 gains the most from ridership of a BART/MUNI Geary tunnel so agency 1 pays for or borrows say 75% of the tunnel costs.Agency 2 with less ridership pays the percentage down to 50% in later years.This is Tunnel arbitrage !