One company I worked for had different divisions specialising in building, roads and concrete and operated across all regions in the country as well as in other countries. These divisions and operations willingly shared resources, and when one area or division was booming they used resources from other divisions that were languishing. This cooperation and sharing of resources enabled the company to almost continually have enough work for all of it's resources and to operate profitably.
The key though, is to anticipate downturns in the region or sectors in which you operate. This means you need to have good market knowledge. In anticipation of a downturn you can avoid taking on additional staff, don't buy new equipment, build up cash reserves, look at diversifying to markets that won't be as negatively affected by the downturn and most importantly adjust margins on tenders in anticipation of a more competitive market and look to securing long duration projects that will get you part way through the downturn.
Operating in a downturn may present opportunities to dispose of old, less efficient equipment. It's also often an opportunity to get rid of poor performing staff. The company needs to look at reducing costs, improving productivity and negotiating with subcontractors and suppliers for better deals and discounts.