From the article it seems the foreign workers are given false information before coming to Dubai, and then their passports are taken (and/or payment withheld) so they can't leave.
It's a global scam where the idea is to make money out of slavery and ensuring profit to every person in the chain, from the sheikh to the so called "travel agencies" and take away the right to complain from the only people who may complain.
The things is that I wrote a school paper years ago on the UAE and back then it wasn't exactly a hidden fact that many workers on the massive construction projects were treated badly.
But then I forgot that not everyone has access to the internet and/or reads human rights reports.
Shame on me.