Exact-dynamics (six-dimensional) quantum simulations of energy-resolved initial-state-selected rearrangement reaction probabilities are presented for H-2(v=0,1,j=0) +OH(v=0,1,j=0) -->H+H2O, at J=0, using the time-dependent reactive-scattering formalism. A few narrow resonances appear at low reaction energies when the H-2 is vibrationally excited, and are shown to be partially associated with the strong-interaction region (in addition to the asymptotic reagents channel, where the potential has an unphysical well). Vibrational excitation of the OH bond is shown to exhibit little influence on the reaction probabilities. Together with similar results due to Zhang and Zhang (J. Chem. Phys., in press), these art the first initial-state-selected simulations of exact-dynamics four-atom molecular reactions.