The tempurature on those units are all about 25-27c / 75C in/out. There is more than enough cooling, the reason the units were spread out was more because of PDU limitations than anything.
Is there some hot air containment or is the whole facility cooled as one?
As stated in a previous statement, there is no wall behind those units, its literally a wall of exhaust fans. 100% of the hot air is kicked out of the facility.
Instead of massive aircraft hangar type DC's, the long, narrow building with wall-o-fans and racks on the long outside walls seems like the most efficient design.