I don't know if this is a known thing but I looked through the leaked manual, page 9.
http://www.scribd.com/doc/121736732/Leaked-Simcity-manual
Click the banner on the main menu to enter the SimCity Store. Here, youll find special add-ons for sale. Select STORE to view the full list of additional game content (both free and paid) that can provide you with new gameplay possibilities
http://www.scribd.com/doc/121736732/Leaked-Simcity-manual