This was a super interesting question, because I was having a discussion about this exact issue but in relation to universities. Universities also have SOME type of racial/sex quota, and they usually abide by them. This is followed by complaints from White students, saying that Black/Hispanic students are getting unfair advantages from affirmative action. But what they fail to consider is that many schools offer that same advantage to White students over Asian students who, by score and gpa alone, deserve a WAY higher percentage of the spots.
So all in all, I believe quotas can help keep a diversified group. At least with colleges; for example, when California State schools removed the quota, the schools were flooded with Asian students. Think of UCLA with 70% Asian students, UC Irvine with more than 80%. After that episode, it seemed like the White students no longer wanted that "fair-treatment" for all students after all.