  An analysis of ages, metallicities, and [alpha/Fe] ratios of globular cluster
systems in early-type galaxies is presented, based on Lick index measurements
summarized in Puzia et al. (2004, Paper I of this series). In the light of
calibration and measurement uncertainties, age-metallicity degeneracy, and the
relative dynamic range of Lick indices, as well as systematics introduced by
abundance ratio variations (in particular variations of [alpha/Fe] ratios), we
find that the most reliable age indicator for our dataset is a combination of
the Lick Balmer-line indices HgammaA, Hbeta, and HdeltaA. [MgFe]' is used as a
spectroscopic metallicity indicator which is least affected by [alpha/Fe]
variations. We introduce an interpolation routine to simultaneously derive
ages, metallicities, and [alpha/Fe] ratios from diagnostic grids constructed
from Lick indices. From a comparison of high-quality data with SSP model
predictions, we find that ~2/3 of the globular clusters in early-type galaxies
are older than 10 Gyr, up to 1/3 have ages in the range ~5-10 Gyr, and only a
few cluster are younger than ~5 Gyr. Our sample of globular clusters covers
metallicities from [Z/H] = -1.3 up to ~0.5 dex. We find that metal-rich
globular clusters show on average a smaller mean age and a larger age scatter
than their metal-poor counterparts. [alpha/Fe] diagnostic plots show that
globular cluster systems in early-type galaxies have super-solar alpha/Fe
abundance ratios with a mean [alpha/Fe] = 0.47+/-0.06 dex and a dispersion of
about 0.3 dex. We find evidence for a correlation between [alpha/Fe] and
metallicity, in the sense that more metal-rich clusters exhibit lower
alpha-element enhancements. [abridged]
