More than once now I have heard the expression "getting into the New World via the Underground" .
'round here, I've only heard this from COs and on convention/assembly programs. (I'm sure some local JWs have used it as well, but i'm neither old nor zealous enough to be having deep conversations with the ones who are likely using it). I think they're trying to coin the expression as a way of preparing people to expect their older loved ones to die before armageddon.