User blog comment:Damac1214/Black Ops 2 Uprising DLC Trailer Released + Double XP on April 12th to April 15th/@comment-5610200-20130404184004/@comment-1937487-20130404203934

Ah, you can run around in that building. It's a bit tricky, but can be done. You just need to be in the sliquifier room and start training zombies around the room in a figure-8 or circle pattern (don't quite remember) although it's a bit hard cos of the tightness, but I managed to get to round 27 with that method... I died because I fell down the elevator shaft when I wasn't paying attention...

In the end though, the only need you have for the bus and elevators is getting around easier. My point still stands; it's optional.