We have developed a coupled-rearrangement-channel method allowing the rigorous non-adiabatic treatment of the multi-channel scattering problem for four particles. We present the study of the binding, resonant and collisional properties of the H̄−Ps system with the total angular momentum J = 0+ (singlet positronic configuration). The binding energy, the life-times of the resonant states and the collisional cross sections are calculated and discussed. We present the preliminary cross sections for the elastic and inelastic H̄−Ps scattering, notably for the excitation of Ps and for the rearrangement reaction producing the H̄+ ions.