Got an answer from Energy Transfer Partners:
"The built in gain schedule in the ET tax package is informational only. If you look on the K-1 itself, you'll see a Box "M" that asks whether or not property with a built in gain or loss was contributed the the partnership during the year. For all of the legacy ETP partners that held through the ETE/ETP transaction, the form of the transaction was a contribution into ETE by all of the public ETP partners of their ETP units (i.e. property and not cash) in exchange for ETE/ET units. Since virtually every ETP partner would have had a difference in the value of their respective ETP units versus their adjusted tax basis, virtually every partner is deemed to have contributed property (i.e. ETP units) with a built in gain or loss (i.e. the difference in the FV of the ETP units immediately before the transaction and the adjusted tax basis of the units). If Box "M" on the K-1 is checked "Yes" (which it should be for virtually every former ETP partner that participated in the ETE/ETP transaction), we are required to attach an informational statement to the K-1".
