The FRA (Draken) and probably calibration is what is referred to as military I guess, and no they couldn't really go else where without a cost to FRA (Draken) setting up new maintenance facilities and possibly penalties being due from the airport if they had too.
Also the improvements to the infrastructure needed to be carried out and were planned for. Why not bring them forward, lessen disruption, lessen the overall cost to the taxpayer through not having to furlough those who worked on the projects and shorten the time frames due to less passengers being in the buildings. Also probably getting better deals as companies wanted the work.
I look at it as a win win all round.