You're mixing apples and oranges.
In the Microsoft case, they were not agency temps. These were people being CALLED contractors when they did not qualify. They had no protection and no agency looking out for their interests.
In your case, these people are employed by the agency (not the case with Microsoft). Just because your company does not provide them with benefits or paid time off does not mean they are not receiving them. Many, many agencies (in fact, by this time I'd say most if not all) provide these benefits to their temps.
If they are dissatisfied with the status quo, it is up to them to do something about it, not you. They know what benefits they receive from the agency. You don't.