A microscopic approach to the problem of charge transfer-induced spin transitions in a system of interacting trinuclear Fe-Co-Fe clusters, which takes into account the switching of polarization during the transformation FelsII-ColsIII-FelsIII→ FelsIII-CohsII-FelsIII (ls-low spin, hs-high spin), has been developed. The cooperative electron-deformational and dipole-dipole interactions and the intracluster electron transfer have been proved to govern the observed significant changes in the magnetic and polarization characteristics of the examined system. The role of intra- and intercluster interactions in the spin transformation has been elucidated. On the basis of the developed approach, an explanation of the temperature dependence of the magnetic susceptibility and of the polar-nonpolar transformation in the {[FeTp(CN)3]2Co(Meim)4}·6H2O compound in response to thermal stimuli has been given.