Verizon Communications Inc. reported a dozen cases of sabotaged cable lines and warned of delays in repairs and customer service on the second day of a strike involving about 45,000 employees. The telecommunications company said there have been 12 acts of sabotage to telephone lines and to Internet and television services in Massachusetts, Maryland, New Jersey, and New York since the strike began. Fiber-optic lines were intentionally cut in Tewksbury and several other municipalities on the East Coast, the company said.