In the Level 3 and Global Crossing's assessment of the transaction, they said it is expected to create annualized adjusted EBITDA synergies of about $300 million and capital expenditure reductions of about $40 million. Level 3 expects to realize about two-thirds of the run rate adjusted EBITDA synergies within 18 months of closing, it said, and it estimated that the net present value of the potential synergies would approximate $2.5 billion. About 39% of total expected synergies are from network expense savings, and about 49% from operating expense savings, with the remaining 12% from reductions in capital expenditures.

"The company expects to incur approximately $200 to $225 million of integration costs associated with this transaction," Level 3 said, with about 55% of the costs from operating expenses, and 45% from capital expenditures to support integration activities.

The companies expect the deal to close by the end of the year. The acquisition is subject to regulatory approval, including possible reviews by the U.S. Department of Justice and the U.S. Federal Communications Commission.