Lensing B-mode power spectrum obtained by cross-correlating the B^lens templates with the corresponding fiducial B-mode simulations (top), and residuals with respect to the model (bottom). Top: averaged BB^lens band-powers using the apodized B70 template mask, with multipole bins of Δℓ ≥ 100 (blue points). The error bars are the standard deviation on the mean of the band-power estimate set. The dark blue curve is the fiducial B-mode power spectrum of our simulations, which assumes r = 0. Bottom: BB^lens band-power residual with respect to the fiducial model, given in units of the 1σ error of a single realization. For comparison, we also show the band-power residuals obtained without masking, as discussed in Sect. 5.1 (red points). Dashed lines show the ± 1σ range of 100 realizations, indicating the precision level to which we are able to test against bias.