It's the other way round - if a company is committed to a path of fairness but has inherited an unfair legacy of salary disparity (this can happen in many ways and is not always because of overt unfairness) then transparency can make it harder for the company to fix the problem.
A good example of transparency not helping is our sudden transparency about the activities of the NSA. Obviously that's not helping them. Though arguably it is helping us.
In a case where a company is intrinsically unfair to its employees and can't correct that, transparency would probably hurt the company but help all the employees - by sending a strong message that it's time to get the hell out of this crappy company.