  We report magnetoresistance (MR) measurements on MgB2 and the corresponding
full account from ab-initio calculations; we suggest that this combination can
be a useful tool to probe electron- phonon coupling. We obtain good
quantitative agreement between high field measurements on neutron irradiated
epitaxial thin films and calculations within Bloch-Boltzmann transport theory
over a wide range of magnetic fields (0-28 T) and temperatures (40-300 K), and
as a function of the field orientation. The crossovers between in-plane and
out-of-plane MR, experimentally observed as a function of either disorder or
temperature are well reproduced indicating that disorder and interaction with
phonons strongly affect the scattering rate of s-carriers.
