This, no?
Here is more on that
http://www.nytimes.com/2014/03/18/world/asia/malaysia-airlines-flight.html?_r=0
http://www.cnbc.com/id/101501652
No, not really. I used to work for the company that developed and hosts the ACARS system. I routinely sent ACARS messages to flight crews that would range from simple ATC instructions to something like hey you left your wallet at home. Its basically a text messaging service.
It would really depend on what ACARS service the airline subscribed to. From the news reports it would seem as though they were getting routine status updates from the aircraft. Since they were over the ocean it would appear that those ACARS messages were being sent through INMARSAT (satellite) rather than over typical VHF/VOR frequencies. That would be the "pings" that they were able retrieve.
Separately, Rolls Royce provided a similar service that would send status reports of the engines. Again, from the news reports, it would appear that Malaysia declined that service since they were getting status updates through ACARS. It would also appear that RR was still able to retrieve the "pings" from that service although it did not contain any information - they were just able to determine that the engines were on. (sort of like roaming on a cell phone)