But companies must follow certain rules to gain REIT status. Such a trust must hold at least 75 percent of its assets in real estate and generate at least 75 percent of its income from property rents or interest on real estate financings or sales. Rather than retaining the income they earn and paying taxes on it, REITs pass along 90 percent of their income to shareholders, who then pay taxes. This means these companies have little in the way of taxable income.

Traditionally, REIT tax treatment could be applied only to assets with physical characteristics: “inherently permanent structures,” according to tax rules. But last May, the Treasury and the I.R.S. proposed new regulations clarifying what constitutes an eligible asset for REIT purposes, seeking “to balance the general principle that common terms used in different provisions should have common meanings.”

The new rules say real estate assets may include microwave transmission, cell and broadcast towers as well as parking facilities, bridges and tunnels, railroad tracks, transmission lines, pipelines and storage facilities. (The Treasury is accepting comments on these rules until Aug. 12; a public meeting is scheduled for Sept. 18.)

Robert Willens, an expert on taxes and accounting and author of The Willens Report, predicted that electric utilities, cable operators and other telecoms would most likely join the REIT ranks as a result of the I.R.S. stance.

But Mr. Willens also said the I.R.S.’s decision allowing the Windstream spinoff to be tax-free meant that almost any company whose business involved real estate would be able to reduce its tax obligation by shifting taxable income derived from those assets to a nontaxable REIT entity. “Any sort of business in which real estate is an important factor — retailing, for example — could separate the real estate from the operating business on a tax-free basis,” he said. “So it strikes me as almost unlimited what can be done here.”

How much in tax savings are we talking about? Significant amounts. By putting its network into a REIT, for example, Windstream will not have to pay taxes on $650 million in revenue. Given that its most recent annual financial filing estimated its tax rate to be 38 to 39 percent in 2014, the spinoff could mean savings of around $250 million in one year. The I.R.S. does not discuss its rulings on taxpayer matters.

David Avery, a Windstream spokesman, said its spinoff into a REIT was not driven by the tax benefits. The transaction “will enable additional investment in our business and create additional growth and jobs over the long term,” he said.