According to the a Siemens press release, the company will provide Atlanta with 4 streetcars at a cost of $17.2 million.  Also this…

The first car is expected to be delivered in September 2012 with revenue service beginning in early 2013. These will be the first streetcars in Atlanta since 1949 and will mark Siemens entry into the streetcar market in the United States.

…The four new streetcars are based on the proven Siemens S70 light rail vehicle platform, which was designed in the United States and is in operation in cities such as Houston, Charlotte, San Diego, Portland and Salt Lake City. The streetcars were purchased through an existing contract with the Utah Transit Authority and will be customized to meet Atlanta’s operating environment. The streetcars are fully upgradeable for future light rail operation as the regional system grows.

h/t: Atlanta Business Chronicle