Complex sentence: Warner formed a partnership with MTV Networks in June 2010 that allowed MTVN to exclusively sell ads on WMG's premium content; in turn, views of WMG videos would be counted as views for MTVN.
Split into simpler sentences: Warner formed a partnership with MTV Networks in June 2010 that allows MTVN to exclusively sell ads on WMG's premium content. In turn, views of WMG videos will be counted as views for MTVN.