Are you sure about this? I've heard conflicting information. I'm in Tepper and Heinz (MBA/MSPPM), and a Heinz classmate said that only Tepper first-years could apply to the dual program. He may have been misinformed, or I may have misunderstood, but the school websites imply that you have to start with MBA classes (e.g., "students may apply to the Heinz School before enrolling at Tepper OR during the 1st year of the MBA program," http://www.heinz.cmu...ness/index.aspx).
To the OP: if the admissions office doesn't already know that you were accepted at Heinz and would definitely attend if accepted at Tepper, please tell them! There's been a surge of interest in the dual-degree program in my class. It would be awesome for there to be enough of us there at once to further shape the program.