Complex sentence: With this sale, WBGH's last ties with WETM were severed since Ackerley already owned WIVT at the time and that station began controlling WBGH when the deal closed.
Split into simpler sentences: With this sale, WBGH's last ties with WETM were severed since Ackerley already owned WIVT at the time. That station then began controlling WBGH when the deal closed.