20% cost overrun is nothing if you look at the typical cost overrun of a US infrastructure project. UES extension in NYC a prime example of that. And 3 years late? How about 50 years late?
So your unions and regulations have nothing to do with it, but it has everything to do with corruption and the way US public command is arbitraged. You probably need _more_ regulation to avoid the former, and have unions involved in the review process (construction workers usually know when a construction company is full of shit).