  We study a disordered superconducting nanowire, with broken time-reversal and
spin-rotational symmetry, which can be driven into a topological phase with end
Majorana bound states by an externally applied magnetic field. As a function of
disorder strength, it is known that the Majorana nanowire has a delocalization
quantum phase transition from a topologically nontrivial phase, which supports
Majorana bound states, to a nontopological insulating phase without them. On
both sides of the transition, the system is localized at zero energy albeit
with very different topological properties. We exploit this deep connection
between topology and localization properties to propose an electrical transport
measurement to detect the localization-delocalization transition occurring in
the bulk of the nanowire. The basic idea consists of measuring the difference
of conductance at one end of the wire obtained at different values of the
coupling to the opposite lead. We show that this measurement reveals the
nonlocal correlations emergent only at the topological transition. Hence, while
the proposed experiment does not directly probe the end Majorana bound states,
it can provide direct evidence for the bulk topological quantum phase
transition itself.
