Then you invest the billions of dollars - either right now, or later when the demand for it becomes too great to ignore. (If I were running the show, I'd try to get out in front of this as much as possible instead of trying to leave someone else holding the bag on this.)
You can't run a 24-hour business with half(?) the means of getting people to your business offline for nearly a quarter of the day. You can't run a 24-hour city with your public transit network crippled like that.
And no, late night buses are not an acceptable replacement. At best, they're a band-aid solution while we find the money for Big Dig 2.0.
Commute -- I know you find it hard to believe -- But the majority of the business in any city is conducted during what we coloquially call business hours -- there is even an acronym with a fairly universal translation:
COB ==5:00 PM local civil time M, T, w, Th, Fri -- thus the COB in Boston most recently was Fri, May, 18 2012 5:00:00 PM EDT the next COB Boston will be ?? (left to the reader as an exercise)
If I told an associate in London (clearly a global 24x7 city) today (not a normal business day in the Western World) that a document was due Monday COB Boston -- he'd be able to translate it into BST without error. The only place I ever have trouble is India with their odd 1/2 hour offset.
As a result of the above -- with the exception of independent contractors, consultants, artistists, philosophers, particle physicists, astronomers (the list is long but finite) the majority of commuters into a city leave @ COB +/- 1 hour or so. Even in the Pentagon most of the commuters leave during the normal rush hour -- with the term skeleton staff describing who is up all night minding the shop.
Note that the primary reason for the T is to take commuters from their residential neighborhoods into and out of the Central Business Districts:
1) Cambridge roughly in a strip along Mass Ave from Harvard to Kendall with Alewife & Leachmere
2) Boston Financial District, DTX
3) SPID
4) Logan
5) Longwood
6) Back Bay along Boyston & Newbury
7) Kenmore / BU
8) Huntington Ave corridor to Heath St.
9) Charles / MGH
10) Government Center
So -- no one ever will spend the B$s necessary to widen tunnels to add parallel tracks soley to accomodate "Night Owls" -- perhaps they will spend the $ -- but only for a different much more compelling reason to the vast majority of the public.
By the way the Tube closes about the same hours as Boston:
from te wikipedia article:
The Underground does not run 24 hours a day (except at New Year and major public events – such as the Queen's Golden Jubilee in 2002 and the Opening and Closing Ceremonies of the London Olympics in 2012) because most lines have only two tracks (one in each direction) and therefore need to close at night for cleaning and planned maintenance work. First trains start operating from approximately 04:45, generally for shorter journeys such as the Piccadilly line's Osterley-Heathrow only rather than the full length of the line, with the remainder operating by 05:30, running until around 01:00. Unlike systems such as the New York City Subway, few segments of the Underground have third or fourth tracks that allow trains to be routed around maintenance sites. Recently, greater use has been made of weekend closures of parts of the system for scheduled engineering work. Also, the Underground runs limited service on Christmas Eve (with some lines closing early) and does not operate on Christmas Day, except for the shuttle to Heathrow Airport. A limited service is provided on Boxing Day.
