The article doesn't mention what was the scam they did? Anyone know?
The real IRS will send you mail if you owe back taxes, and instruct you to call them.
Didn't you think you were calling a government office? They aren't exactly known for their customer service, whereas scammers are known for having a slick feel to their operation. Interesting that that was your tip off.
You probably would have figured it out as soon as they told you that you could settle your IRS debt with iTunes gift cards.