Tunnel Arbitrage to fund a Geary street MUNI/BART subway

I to enjoy blogging about bay area mass transit and light rail and subways, most of my blogging as to about the economics of tunneling for multiple systems such as MUNI/BART under Market street. What is that economics? digging two or more tunnels would cost more right? but would cost twice as much or less.Can two or more agencies share costs and/or loan to one another parts of the costs? I call this on my blog TUNNEL ARBITRAGE 🙂 This would be shared costs of some percentage (?) and one agency owes the other payment on bonds or future taxes for a portion of that percentage. California high-speed rail even proposed private-public partnerships where the infrastructure and even the rolling stock might be leased from a for-profit firm, I discuss my response to their RFP here https://yellowdragonblog.com/2015/07/28/utilizing-a-esop-to-capitalize-infrastructure-for-california-high-speed-rail/ As to the Tunnel arbitrage I discuss that here https://yellowdragonblog.com/2014/11/19/vtabart-and-california-high-speed-rail-potential-synergies/ My thoughts are a common tunnel under Geary for MUNI/BART/CHSR need not run all the way to the beach so MUNI would borrow and/or share the tunnel costs with BART to some well-studied midway point and head south.South might mean 19th avenue and even here this tunnel could be a two-decker with MUNI?

More discussion here http://hoodline.com/2016/12/sf-transit-agencies-say-brt-improvements-will-set-stage-for-future-rail-line-on-geary