If its a completely different location, you don't need to use setpos ... just set up the scene there as you want it to be. The units from the first part of the intro won't get in the way. Obviously you can make camera shots anywhere, so just film the second part in the usual way.
If the locations are close you can still use a second set of units. However you would then have to deleteVehicle the first lot so that they don't get inthe way.
A blackout, titletext "some hours later", and a blackin is probably the best way to cover the sudden changes, which obviously happen during the blackout.