In this paper, we present results on transverse mass spectra and Hanbury-Brown and Twiss correlation functions of negatively charged hadrons, which are expected to be mostly π^-, measured in Pb-Pb collisions at 40 A GeV/c beam momentum. Based on these data, the collision dynamics and the spacetime extent of the system at the thermal freeze-out are studied over a centrality range corresponding to the most central 53% of the Pb-Pb inelastic cross-section. Comparisons with freeze-out conditions of strange particles and HBT results from other experiments are discussed.