Re: The Chinese and Russians are going to build it??
There is no business case for the usual railway "connect many places" either.
Railways rarely pay, as Victorian investors found out. And investors in Railtrack found in 2001. Or investors in Eurotunnel found out in 2006. Or investors in LCR found out in 2009 when HS1 became insolvent. And as any private sector investors in HS2 will find out in a few years time.
The fundamental cause of this is that infrastructure is expensive, but the returns it can generate per pound of capital invested are lower than the economic cost of capital (whether public or private). China probably likes the idea of a world spanning construction project because it is currently enduring a nightmare slowdown, vast over-capacity in steel making, cement manufacture and construction. But spending something of the order of $200bn on this tunnel (at Chinese construction costs) would not be justified by snail rail, and if you then need to build 6,000 odd km of high speed links across Russia, Alaska and Canada, then the costs spiral further.
But if China wants to spend all the IOUs from the developed world on this, who are we to tell them otherwise?