Here is confirmation of their spectrum value. Unicel's spectrum license in just the city of Sao Paolo (20 MHz) was valued at $181 Million. Search for the article "Anatel confirms decision to revoke Unicel’s licence" from December. In this article it values Unicel license at this amount. NIHD has a license for 11 of the 13 largest cities in Brazil. If you do the math then their license is worth $2.66 Billion just for Brazil. See calculation below.
Sao Paulo has a population of 11.3 Million. If it was $181 Million for 20 Mhz of coverage for Sao Paulo then the price is $0.80 per Mhz pop (i.e., Mhz per 1 million people). consider what NII's holdings of its 20 Mhz coverage in 11 of the top 13 cities in Brazil are worth. 20 x 196 Million (Brazils population) x 11 cities divided by 13 cities x $0.80 = $2.66 Billion.
They also own broadband spectrum in Mexico, Peru, Chile, another 20 of a different spectrum band in Brazil, and Argentina. And cell phone towers worth $2 Billion.
One issue is that any acquirer would have to deal with their wireless operation which is losing money but given the scramble to get spectrum and towers and the really low price NIHD trades at I'd have to imagine that's not an issue. Especially if they can return it to profitability which happened only 18 months ago.
AT&T did 50 deals in 2012 for spectrum and just bought Alltel for $780 Million and is looking to buy $1.8 Billion spectrum from Verizon. Dish, Sprint, and DirecTV are all scrambling to add spectrum. NIHD is sitting pretty right now with over $10 Billion worth of spectrum.