This is a perfect example (link at bottom) of how the illegal immigration problem should be handled. Charge the businesses that hire them. These businesses not only hurt the nation but also abuse the illegal workers themselves.
What's there to be gained by arresting and detaining a bunch of illegals? These people don't have much money and they return anyways. By going after the businesses that hire them, you dry up the incentive to cross the borders illegally, and the government can possibly recoup the litigation costs.
This is not unlike the war on drugs, where the government fights the losing battle of arresting and incarcerating people with a joint. The real solution is to legalize some milder drugs, like marijuana, then tax them heavily and use the proceeds for public outreach and education.
Of course, all this requires a government with efficiency and integrity, and when is that last we had such governance?