Results of Wannier orbital-based Hartree-Fock and various correlated ab initio calculations using 6-31G** basis sets are reported for the two boron-nitrogen polymer systems polyaminoborane [BNH4](infinity) and polyiminoborane [BNH2](infinity). At the Hartree-Fock level the calculated equilibrium geometries, cohesive energies, polymerization energies, and band structures are virtually identical with those obtained from the standard Bloch orbital-based approach. Electron correlation effects on the investigated ground state properties are discussed within Moller-Plesset second-order perturbation theory and coupled-cluster singles, doubles, and triples theory. For polyaminoborane no bond alternation is found in contrast to previous studies. Correlation corrections to the band structures are considered in second-order Moller-Plesset perturbation theory with third-order localization diagrams included. They lead to a decrease of the fundamental gap of polyaminoborane and polyiminoborane by 40% and 51%, respectively, and reduce the band dispersions.