It's whenever! Really the fake!city's got this mish-mash of horrors going on, so everyone can run into everyone else even if their initial problems get sorted. So like Buffy can run into Martha and they can team up and track down Scott and that crew can bump into the grumpy old men, etc.

BASICALLY it took the aliens a few days/a week to come up with the door/data-scrubber thing, so everyone's got plenty of time to run around surreal nightmare crazyland.

...and we should probably come up with a solid timeline of who showed up when and what happened.