That's right! You can take any plugin model from SC4 (i.e. a building or lot) and use this tool to be able to plop the building in SC2013: http://community.simtropolis.com/files/file/28611-4-to-13-plugin-converter/
From the website:
In a breakthrough development, a group of SimCity modders have developed a means of importing any model originally created for SimCity 4 directly into SimCity 2013, removing the previously thought requirement of access to the original 3D files. This process can be carried out by the end user on their own PC’s via the use of an automated tool, which has been released today at Simtropolis.com.
I can't wait to import all of my buildings from SimCity 4 once I get this game.