Shares of Yahoo (NSDQ: YHOO) are jumping today, following a much talked-about report from Sanford Bernstein analyst Jeffrey Lindsay, arguing that the combined value of Yahoo’s various divisions are worth more than its current market value. He breaks the company down into three businesses, display advertising, search and subscriptions, assigning each a value based on the market value of comparable firms:

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—Display: Based on the buyout multiples at Acquantive, DoubleClick and Right Media, this division could be worth around $25 billion as a standalone entity.

—Search: Pegged at $15.5 billion, based on multiples at Google (NSDQ: GOOG) and Ask.com

—Subscription: $1.3 billion, based on multiples at Match.com, Real Networks and Earthlink (NSDQ: ELNK).

Adding it all together gets you $42.3 billion, which, when added to Yahoo’s cash position and stakes in Yahoo Japan and Alibaba, comes to $54.3 billion ($38/share), far above the company’s current $37 billion market cap ($28/share). Thus, the report argues, if Yahoo management—or, perhaps, a private equity firm—were willing to take the bold step of breaking the company apart, it could immediately unlock significant shareholder value. Ignoring the question of whether the company could feasibly be broken up this way, it’s not clear why the market couldn’t value Yahoo like this under its existing structure.

The report also details another scenario that could result in an even higher value, but it’s much less radical, so it hasn’t been getting as much attention. Basically, he runs the numbers on the trendy idea that Yahoo should outsource its search business to Google, resulting in better monetization of its traffic and an opportunity to reduce headcount. Under this scenario, the company would see a 16 percent jump in revenue and a 16 percent drop in operating expenses, leading to a major spike in profits, as soon as 2008. If management were willing to swallow its pride and take this measure, argues Lindsay, the company’s stock would be worth $45 per share.

Ultimately, Lindsay doesn’t see either of these scenarios playing out. Instead, management is unlikely to do anything drastic, despite its “no sacred cows” promise. For that reason, the report is basically a negative one, describing Yahoo as a company full of locked-up value that’s likely to remain locked up.