Bartz said on the conference call that the companies expect the deal to close by early 2010, after which the companies will move hastily to integrate search and advertising platforms.
Yahoo's search will transition to Bing in all global markets starting with the U.S. three to six months after the deal closes. Yahoo will migrate its advertising network from its Panama platform to Microsoft adCenter fully about a year after close of the deal, she said.
Yahoo's search will be powered by Bing and will say so at the bottom of search pages, but it will continue to be branded by Yahoo, Bartz said.
The companies are prepared to argue their case for a swift close to the deal to regulators in the U.S. and Europe, since they expect Google to protest it, Ballmer said.
"We suspect we'll face some opposition from the competitor who may not like more competition," he said. "This is one of those cases where us coming together will provide more competition to the market leader, not less. We'll expect the competitor to be aggressive."
However, Ballmer said the companies have a good case as to why the deal improves competition and will overall provide benefits to consumers, advertisers and publishers by creating a more viable alternative to Google than the companies were independently.
David Mitchell, senior vice president of IT research at analyst Ovum, said it's unlikely that regulators in either Europe or the U.S. would intervene given that neither Microsoft nor Yahoo hold large shares of the online advertising market.
However, regulatory opposition can't be ruled out. The deal could be viewed as allowing Microsoft to become too dominant overall given its strength in areas such as operating systems, Mitchell said. But "my personal view is that it would be very difficult for regulators to sustain that as a defensible position," he said.
As two smaller players in search-based advertising, Microsoft and Yahoo should both derive great benefits from the deal, said Rebecca Jennings, principal analyst at Forrester Research. This will turn them into a powerful second player behind Google and could spark a price competition between the two, she said.
Once the deal closes, Microsoft's share of the online advertising market will jump from 8 percent or 9 percent to 30 percent or so in the U.S., she said. The U.S. market is estimated to be worth around $15 billion this year, growing 15 percent a year to as much as $30 billion by 2014, she said.
Yahoo benefits by no longer needing to invest in a search engine, which was not gaining traction against Google anyway, Jennings said. Since the deal gives Yahoo 88 percent of the revenue from the sites it operates, it means Yahoo can concentrate on its strengths, such as display advertising, she said.
Sign up for MIS Asia eNewsletters.