"Cash flow stability has improved in the telecoms sector, and stable operations is what private equity is looking for traditionally," said S&P analyst Todd Rosenbluth.
Analysts had previously said Alltel could be sold for $25 billion to $30 billion, with other potential buyers including industry rivals such as Verizon Wireless, a venture of Verizon Communications and Vodafone Group; AT&T, and Sprint Nextel.
But no such strategic suitor emerged. S&P said on Monday it does not expect a counterbid from another telecommunications company, as some carriers might not see a good technology fit and others likely would see Alltel as too expensive now.
Reuters previously reported that Providence Equity Partners and The Blackstone Group had teamed up for a bid for Alltel. The Carlyle Group and Kohlberg Kravis Roberts & Co. <KKR.UL> also had forged a team to explore a potential offer, other sources said on Monday.
The company disclosed during an earnings conference call in February that it was reviewing its strategic options. Media reports from as early as December 28 had said private equity firms were eyeing the company due to its relatively low debt.
Alltel is the largest U.S. regional wireless company, with around 12 million customers, compared with national carriers AT&T and Verizon, which each have over 60 million wireless subscribers.
It provides services in parts of 35 states, although roaming agreements with its competitors help it offer coverage around the country.
Alltel reported first-quarter profit from current business, excluding items, rose to $225.4 million, or 63 cents a share, from $168.57 million, or 43 cents a share, in the year-ago quarter.
Private equity firms typically buy companies and sell them a few years later, borrowing most of the money to make their purchases. A frothy debt market has fueled a massive wave of leveraged buyouts in the last two years.
In the last few weeks alone, automaker Chrysler Group, contact lens company Bausch & Lomb, and credit card processor Alliance Data all agreed to be bought by private equity firms.
Analysts said buyers would likely seek a way to improve Alltel's operations, boost returns before taking the company public or selling it to another telecoms company.
The Little Rock, Arkansas-based company had spun off its traditional phone business in July of last year to form Windstream, a move that analysts said was to prepare for a buyout.