Two exchange operators have swapped roles in a recent deal, with the expected acquirer acting as a target and vice versa.

CBOE Holdings (CBOE) - Get Report , the operator of Chicago Board Options Exchange, has agreed to acquire Bats Global Markets (BATS) for $3.2 billion. CBOE will pay 31% in cash and the rest in stock.

According to Bats' officials, the company did not participate in an auction process.

"Bats found a strategic relationship that was unparalleled," company CEO Chris Concannon said during a Monday call with analysts. "It's rare to find two companies that have such complementary business models."

According to analysts, the deal is surprising in that Kansas City, Kan.-based Bats was expected to be a buyer in the exchange space, while CBOE was considered a more likely target for takeover.

"Since CBOE went public in 2010 it has been viewed as a potential take-out candidate, given its generally singular product focus (options), relatively small size, and differentiated proprietary product lineup," analyst Daniel Fannon of Jefferies wrote in a note. "The pivot to being the buyer is interesting but makes sense if management is looking to compete more globally."

For its part, Bats Global just went public in April in its second attempt at listing on the stock exchange.

"It's actually kind of surprising," analyst Larry Tabb of the Tabb Group said by phone. "They're a really good exchange organization. They run very tight, quick and efficient markets, and have done so since they started around 2000."

Bats made an attempt to go public in 2012, but its computer system was overwhelmed and virtually failed. The April offering included 13.3 million shares at $19 each, a boost from the original offering of 11.2 million for $17 apiece.

The deal is likely a positive for Bats and the industry generally, said Andrew Bond, an analyst with RBC Capital Markets.

"A Bats acquisition would likely be a bottom in multi-list options pricing, as Bats has been the primary driver of compression over the past five years," he wrote in a note to clients. "In this regard, the multi-list business becomes more attractive and CBOE would have more than 30% market share, becoming a leader in both the price-time and pro-rata segments."

In addition to Bats' recent listing, its activity in the deal market had made it seem an unlikely takeover target. On Aug. 11, Bats acquired New York-based Javelin for an undisclosed amount, and in March, it bought ETF.Com, an ETF news provider.

More than a year ago, in January 2015, the firm purchased Jersey City, N.J.-based foreign exchange market Hotspot FX from KCG Holdings for $365 million.

CBOE, meanwhile, acquired all-electronic National Stock Exchange in 2011. No terms were disclosed.

While Tabb noted that the transaction moves CBOE "into the equities business," Bond pointed out that it will increase the company's "exposure to highly competitive asset classes that are in secular declines, such as multi-listed options, U.S. equities and European equities."

Another obstacle is that the two companies don't have meaningful synergy opportunities because Bats already had a lean operation, and the firms have very different corporate cultures.

Bank of America Merrill Lynch and Broadhaven Capital Partners, LLC are acting as co-lead financial advisers to CBOE Holdings.

Bank of America's team included Kaivan Shakib and Kevin Brunner, while Broadhaven's included Gerard von Dohlen and John Simpson.

Bank of America Merrill Lynch will also provide CBOE with financing.

Sidley Austin's Leonard Ng, Caitlin McErlane, Oliver Lewis and Kristina Nordlander provided legal advice for CBOE, whose in-house team included Joanne Moffic-Silver, the general counsel, and Patrick Sexton, the deputy general counsel. 

Barclays Capital acted as lead financial adviser to Bats, while UBS Investment Bank acted as co-financial adviser. Davis Polk & Wardwell's Leonard Kreynin served as legal counsel. 

CBOE, which has a market cap of $5.51 billion, was trading at $67.78 per share Monday, down 3% from market's open.

Bats, which has a cap of $2.96 billion, dropped 3% to $30.73 per share.