  We prove that, in any flavor transition, neutrino oscillation CP violating
asymmetries in matter have two disentangled components: (a) a CPT-odd
T-invariant term, non-vanishing iff there are interactions with matter; (b) a
T-odd CPT-invariant term, non-vanishing iff there is genuine CP violation. As
function of the baseline, these two terms are distinct L-even and L-odd
observables, respectively. In the experimental region of terrestrial
accelerator neutrinos, we calculate their approximate expressions from which we
prove that, at medium baselines, the CPT-odd component is small and nearly
$\delta$-independent, so it can be subtracted from the experimental CP
asymmetry as a theoretical background, provided the hierarchy is known. At long
baselines, on the other hand, we find that (i) a Hierarchy-odd term in the
CPT-odd component dominates the CP asymmetry for energies above the first
oscillation node, and (ii) the CPT-odd term vanishes, independent of the CP
phase $\delta$, at E = 0.92 GeV(L/1300 km) near the second oscillation maximum,
where the T-odd term is almost maximal and proportional to $\sin\delta$. A
measurement of the CP asymmetry in these energy regions would thus provide
separate information on (i) the neutrino mass ordering, and (ii) direct
evidence of genuine CP violation in the lepton sector.
