  We study generation of two-dimensional dispersive shock waves and oblique
dark solitons upon interaction of tilted plane waves with negative refractive
index defects embedded into defocusing material with linear gain and two-photon
absorption. Different evolution regimes are encountered including the formation
of well-localized disturbances for input tilts below critical one, and
generation of extended shock waves containing multiple intensity oscillations
in the "upstream" region and gradually vanishing oblique dark solitons in
"downstream" region for input tilts exceeding critical one. The generation of
stable dispersive shock waves is possible only below certain critical defect
strength.
