In a paper by Ashtekar et al in 2013 on the approach to the final state to a stationary black hole they study the evolution of the multipole moments of dynamical horizons, which relax away (except for mono and dipole moments) to a stationary horizon and merges with the event horizon. They state that this is due to mass and gravitational waves entering the horizon from outside the event horizon. They speculate that those gravitational waves arise and may have some correlation to others that radiate to infinity from outside the horizons that we'd see during the final stage of black hole formation or mergers of two black holes (e.g. the merger and ring down phases). Dynamical horizons are similar to apparent horizons but they argue theirs is a covariant description (apparent horizons depend on the foliation used). They mention that possibly the grav waves we see at infinity may tell us something about the multipole moments of the dynamical horizon, in a completely non quantum description. It seems this would mean that information is extracted from the black hole.