What role will underground bases play in sequestering humans for continued experimentation by alien Greys if human annihilation is enacted?

This is yet another utility of having large underground installations capable of housing many, many individuals. It is indeed part of the plans in the event of an annihilation to sequester a core group of humans of interest to the alien Greys for their Genetics Program to continue the lineage for a time with the intention of reaching their goal of figuring out the human genome and the origin of our ability to reincarnate as the same person, if in a different setting with a somewhat different genetic complement. The alien Greys see this as an interesting capability they wish to emulate and do not understand that it is a soul-based characteristic and requirement for reincarnation to happen in this way, and that it could never apply to them simply by borrowing some of human DNA to more closely resemble human, and that is because these are soulless beings. So even the entire human genome, if co-opted and spliced together, would not connect to a soul and thus become immortal and allow incarnation with a continued life being lived again and again. So this would be very much a slave colony and not a reprieve or a desirable safe harbor for humans to avoid the annihilation event and allow them to continue. No one living under the control of the alien Greys would be happy and it would add more grievous harm to the negative karma they have already endured through many lifetimes in earth plane, so it would represent a downward spiral and essentially a dead end for those beings with respect to any progress with their soul journey lived out among the alien Greys as guinea pigs.