I can imagine no other organization more capable of following the letter of the law - if not the spirit - than a group of lawfirms.

It's not collusion if every other firm raises salaries only to remain competitive, and I doubt many people are complaining about higher salaries. The companies you mention had secret no-hire agreements in place.

Why would companies collude to raise salaries? If other law firms did not raise salaries to remain competitive, that would be suspicious, especially if the firm that did mysteriously lowered them again a short time later.

One rule for lawyers one for the little people