Apparently these guys are not even very good scammers as  it seems the people that call them back don't actually speak to anyone anyway.  How are you going to properly scam someone if you don't answer your phone?

Same thing here ... computerized female voice claiming to be IRS.  I didn't call back - Googled the number and found this before I did anything.

I also received a call from this number. It was a automated female voice saying that the IRS was filing a lawsuit against me. The message gave a number to call for more information (347)560-5677. I called the number and received a busy signal. I figured this was a scam.

Idiots!!!

I too was notified of a lawsuit filed by the IRS so I went to the IRS website. This is on the IRS.gov website on how to report phishing scams.
You receive a phone call from someone claiming to be from the IRS but you suspect they are not an IRS employee ... 1.Record the employee's name, badge number, call back number and caller ID if available.
2.Call 1-800-366-4484 to determine if the caller is an IRS employee with a legitimate need to contact you. •If the person calling you is an IRS employee, call them back.
•If not, report the incident to TIGTA and to us at phishing@irs.gov (Subject: 'IRS Phone Scam')