  (Abridged) The prevalence of radio-loud AGN activity in present-day massive
halos is determined using a sample of 625 nearby groups and clusters from the
SDSS. Brightest group and cluster galaxies (BCGs) are more likely to host a
radio-loud AGN than other galaxies of the same stellar mass (by less than a
factor of two at a stellar mass of 5e11 M_sun, but over an order of magnitude
below 1e11 M_sun). The distribution of radio luminosities for BCGs does not
depend on stellar mass, however, and is similar to that of field galaxies of
the same mass. Neither the radio-loud fraction nor the radio luminosity
distribution of BCGs depends strongly on the cluster velocity dispersion. The
radio-AGN fraction is also studied as a function of clustercentric distance:
only within 0.2 r_200 do cluster galaxies exhibit an enhanced likelihood of
radio-loud AGN activity, approaching that of the BCGs. The radio-loud AGN
properties of both BCGs and non-BCGs can naturally be explained if this
activity is fuelled by cooling from hot gas surrounding the galaxy. Using
observational estimates of the mechanical output of the radio jets, the
time-averaged energy output associated with recurrent radio source activity is
estimated for all group/cluster galaxies. Within the cooling radius of the
cluster, the radio-mode heating from the BCG dominates over that of all other
galaxies combined. The scaling between total radio-AGN energy output and
cluster velocity dispersion is considerably shallower than the sigma^4 scaling
of the radiative cooling rate. Thus, unless either the mechanical-to-radio
luminosity ratio or the efficiency of converting AGN mechanical energy into
heating increases by 2-3 orders of magnitude between groups and rich clusters,
radio-mode heating will not balance cooling in systems of all masses.
