Doesn't sound like a legit reason to me at all. If they're not breaking environmental laws, then why are they so worried about being sued for it? If the lawsuit is frivolous and baseless,it will fall apart on its own and the gov't can counter-sue for legal expenses.
Because they want to build the bridge in the next 10 years not the next 30. The asshole that owns the Ambassador Bridge will do everything he can to try and hold onto his hugely profitable local monopoly. Which covers funding pointless lawsuits ment to hold up construction of competition
Would you pass a law exempting someone from the criminal code on the basis that they might be falsely accused of a crime some day?
Criminal law is very different than a civil lawsuit. No need for that sort of protection.