"And even if a policy is fully legal and above board, it doesn't necessarily mean it's sensible, just, or effective.   Say a company submits the best bid for rebuilding a bridge and even does a decent job on that project.   Automatically handing over all other such projects (not to mention totally different kinds of projects) to that company for several more years on a no-bid basis is an unwise practice and one wildly open to abuse." - Genie

Now the Government Departments requiring this work to be done takes your advice Genie and puts the next job for the US Military out in Iraq or Afghanistan out for Competitive Tender. You have say four bidders:

Contractor A - Did the last bit of work there, already has all security vetting of personnel and clearances in place, has plant and personnel on site, or at least in the area, are fully familiar with operating routines and systems.

Contractors B; C & D - Fully capable of doing the work, all personnel have to go through security vetting to get required clearances, all their plant and equipment must be hired locally or transported to site, once on site they must allow time for aclimatisation and familiarisation with operating routines and systems.

Now all those facets of the job are cost items that have to factored into the bids - You tell me which contractor is best placed to put in the most attractive bid in terms of cost; effectiveness; degree of comfort to the Client. My money would be on Contractor A.