I'm wondering if this is supposed to be the very distant past. None of that architecture
really screams NYC to me, but it almost seems like we're supposed to think it is purely for speculation reasons. I always got the impression with the old BSG, that when they finally found Earth they would be revered as the Gods whose callsigns they had. I thought that might be a cool idea with this one too. But who knows.
One of the reasons I think this is the distant past, is that the 13th tribe was supposed to have left Kobol
2,000 years earlier. That would have meant that they either arrived on a post-apocalyptic (far future) Earth themselves, or arrived around the time of Jesus. But none of this would really work, since it wouldn't make sense for them to have arrived while there were already humans here. But if this was supposed to be the distant past (say 50,000 years ago), they could be the origin of human life on Earth.
My prediction:
The 13th tribe has been destroyed to the point where they have reverted to a more primitive civilization. The new humans will be regarded as Gods, giving rise to some of our real world religions. The Enemy cylons will arrive and there will be a massive battle (the kind you hear about in mythology and religion). All ships will be lost and everyone will be marooned on Earth with no advanced tech. Human history takes over from there. This also provides a bit of the cautionary message that BSG has become known for. Obviously this is ridiculously simplified, but that's my guess.
All this has happened before, and it shall happen again.