  We investigate a model for the CuO_2 plane of high-T_c superconductors where
the charge carriers are coupled to A_{1g} and B_{1g} symmetric out-of plane
vibrations of the oxygen atoms in the presence of local Hubbard correlations.
The coupling is implemented via a modulation of the hopping integral and we
calculate the renormalization of vertex and pairing scattering functions based
on the time-dependent Gutziller approximation. Contrary to local
electron-phonon couplings we find that the transitive coupling can even be
enhanced by correlations for certain momenta and symmetries of the vibrations.
While this effect may be important for certain properties, we find that, with
regard to superconductivity, electron-electron correlations still generically
lead to a suppression of the pairing correlations. Our results allow for an
estimate of correlation effects on the electron-phonon induced pair scattering
from weak electron-electron interactions up to the Mott regime. For onsite
repulsions relevant to cuprate superconductors our calculations reveal a
significant contribution of B_{1g} phonons to d-wave superconductivity.
