I doubt that they would need a hangar for this job regardless it would appear that no hangar on the airport would be capable of handling the 777 other than maybe the Sands hangar which is probably not available at any price. The Boeing teams have worked in much worse conditions so I don't see lack of a hangar being a deal breaker. LAS weather is cooling down and quite nice at this time of the year. Hard to imagine the airport authority denying them permission to do the work on the freight ramp but whatever