If you are in the U.S. and wish to bid public sector work, you should be aware of the Brooks Act, which requires government agencies to discount the importance of price for architectural, engineering and construction design work.? The Brooks Act, not surprisingly encourages an environment where successful incumbents are difficult if not impossible to dislodge.? While the Act applies to the design professionals rather than contractors, obviously if you are bidding public work, you will want to have good relationships with the architects and engineers on the inside, and even if they are playing things fairly, you still will find many cases where the Brooks Act approach is applied, often informally, in setting conditions so that public agencies select the contractors they trust and respect, more on work quality than actual bid price.
You can find some more insights into this matter at the? American Council of Engineering Companies site.