It's all about 2013 earnings, which are estimated to nearly double.
Even with CMLP's historically high 42.08 P/E, 88%-plus growth in 2013 gives it a low 2013 PEG of .47, and makes it appear undervalued on a 2013 PEG basis.
This, coupled with the 8%-plus yield, are most likely what's driving CMLP's 2013 price gains.