Motorola had $3.2 Billion in cash, and its losses act as tax deductions for Google (8yrs * $700 million = ~$5.6 Billion, from the article). 12.5 - 3.2 - 5.6 = $3.7 Billion.
The amount of unused tax benefits MM has is $1.7 billion according to the article - the $700 million a year figure is speculation by an analyst.
Furthermore, future tax benefits ought to be discounted to a current value and the potential rate of return for alternative investments for Google's cash must be considered.
Not to mention that Microsoft's $250 million also affects their taxes.
http://www.reuters.com/article/2011/08/31/us-motorolamobilit...
Motorola had $3.2 Billion in cash, and its losses act as tax deductions for Google (8yrs * $700 million = ~$5.6 Billion, from the article). 12.5 - 3.2 - 5.6 = $3.7 Billion.