  {We simulate the evolution of relativistic electrons injected into the
intracluster medium by five radio galaxies. We study the spatial transport and
the emission properties of the injected radio plasma over a $\sim 5$ Gyr
period, and the sequence of cooling and re-acceleration events experienced by
electrons, using a Lagrangian approach joint with a numerical method to model
the evolution of momentum spectra of relativistic electrons. When compared with
electrons injected by shock waves, electrons injected by radio galaxies (here
limited to a single injection event) in our tests are unable to fuel large,
$\sim \rm ~Mpc$ sized radio relics with fossil electrons, as required by
current theoretical models, while electrons previously seeded by other shocks
can do this. On the other hand, the combination of seeding from radio galaxies,
and of re-acceleration events from plasma perturbation, can produce detectable,
small scale and filamentary emissions in the proximity ($\leq 100-200$ kpc) of
radio galaxies.
