Were the engineering companies unethical, YES.
Were the government officials unethical, YES.
Does this happen every day, Unfortunately YES.
I have been working in State government for over 20 years as an engineer. In some ways, the ethics that "normal" working employees vs. the ethics of elected officials is ridiculous. There have been times during my career that we were told that we couldn't even accept a drink (e.g., bottled water, soft drink or coffee) at a facility during a meeting. At the same time, companies are giving tons of cash to political campaigns, and they later receive multi-million dollar contracts. I don't know about you, but common curtsey (e.g., a drink) is not going to unduly influence my decision towards a facility; but I would think that a major financial contribution could influence someone who's an elected official (even more so if the money went straight to the person's bank account).