We compute the real part of the 2-loop vertex corrections for charmless
hadronic B decays, completing the NNLO calculation of the topological
tree amplitudes in QCD factorization. Among the technical aspects we
show that the hard-scattering kernels are free of soft and collinear
infrared divergences at the 2-loop level, which follows after an
intricate subtraction procedure involving evanescent four quark
operators. The numerical impact of the considered corrections is found
to be moderate, whereas the factorization scale dependence of the
topological tree amplitudes is significantly reduced at NNLO. We in
particular do not find an enhancement of the phenomenologically
important ratio |C/T| from the perturbative calculation.