I think it was Howard Storm who was given the idea that God is always creating.
Scientist are saying that there is something like another universe, on the other side of the big bang in which time is going the other way, backwards.
As philosophy would have it, God is not bound by time, so it is not like he is done creating, nor starting to create, nor waiting for anything to respond to his beginning it, except from our perspective. When he created the Bride of Christ, the Dwelling Place of God, he spoke her into existence, complete, with a word, but it has taken this many years of suffering, trial and living this temporal existence, to complete, seen from our point of view.
Time therefore has no particular significance in God's economy; 'before', applied to God, is about causation, not time.
As for the negative universe notion, it is fun, but that gives [balanced] proportion where, as I understand it, proportion did not exist. It would put the big bang at the edge of both universes, when (as I understand it) science says there is no direction we can point to and say, "it was over there."