In New York at least, constructions unions extract large amounts of money from the government. Some examples that come to mind:

  * Lots of construction employees are mandated by unions to stay around (crane greasers I believe are an example) even though these employees do no work, and then managers have to be hired to manage more employees, etc.
  * Sometimes employees are hired to do no work at all
  * Highly experienced employees will be given menial jobs like coffee-fetcher sort of deal, but get paid very highly for it due to their experience.
  * The MTA has no negotiating power, the unions and the construction contractors agree on a price and then give it to the MTA

Why is it like this? I don't know, one could imagine all sorts of corruption, political plays to get the construction vote, political games to avoid seeming anti-union, who knows.