In SSMS 2012, when the known shortcut to open the window to enter the values for Template Paramenters is not enabled upon installation, the menu item Query-> "Specify Values for Template Parameters: does not have a shortcut assigned:

 

To enable this option, you need to go to the menu: Options -> Keyboard and change the keyboard mapping scheme from "Default" to "Visual Studio 2012 Compatible":

 

 

After making the change, the shortcut is visible in the Query menu item and it should work as in previous versions of SSMS: