NEW YORK, Jul 09, 2014 (BUSINESS WIRE) --SFX Entertainment, Inc. SFXE, -2.49% and T-Mobile US, Inc. TMUS, -1.94% today announced an expansion of their previously announced marketing partnership, with T-Mobile becoming a sponsor of SFX’s most iconic festivals: TomorrowWorld, Electric Zoo andMysteryland, in 2014 and 2015.