  We investigate the Fano-type line shape of the Ba mode of
Y_{1-x}Ca_xBa_2Cu_3O_{6+y} films observed in Raman spectra with A_1g symmetry.
The line shape is described with an extended Fano formula that allows us to
obtain the bare phonon parameters and the self-energy effects based on a
phenomenological description of the real and imaginary part of the low-energy
electronic response. It turns out that the phonon intensity originates almost
entirely from a coupling to this electronic response with negligible
contributions from interband (high-energy) electronic excitations. In the
normal state we obtain a measure of the electron-phonon coupling via the
mass-enhancement factor lambda. We find lambda=6.8 +/- 0.5 % around optimum
doping and only weak changes of the self-energy in the superconducting state.
With increased disorder at the Ba site we find a decreased intensity of the Ba
mode which we can relate to a decreased electron-phonon coupling.
