Recent developments in COPV (Composite) tanks may make LN2 a viable fuel.
The Govt and DOT regulations are antiquated and need to be updated.
Lincoln composites makes Tuff tanks supporting operating pressures of 950 Bar (13500 psi).
Quantum (http://www1.eere.energy.gov/hydrogenandfuelcells/pdfs/04_warner_quantum.pdf) has DOT and EIHPII type IV tanks approved at 10000 psi.
Spherical Type V tanks have been designed and tested supporting 2000 Bar Working pressures by Nasa.
These next generation tanks only require 150psi input pressure for filling... They have sensors in the fiber and internal regulators. Very slick technology developed and tested over 50 years in our space programs.
Pressurized LN2 Dewars support venting N2 up to 350psi and can be used to fill these type V vessel directly.
We now have technology that allows us to store 8,000L / 8 cubic meters of n2 gas in a 10cm radius high pressure spherical tank weighing 6kg at 2000psi. About the size of a basketball.
We have DOT approved technology (for hydrogen) that allows us to store 4,000L / 4 cubic meters of n2 gas at 10,000 psi.
With these new transportation and storage options can LN2 now be useful as fuel?