[1andrew1]

I imagine mobile providers' costs are pretty fixed with marginal costs going up in steps when additional capacity is needed.

I think the issues include the fact that mobile networks don't operate 100% owned subsidiaries in every country. Many networks like T-Mobile, Telefonica O2 and Vodafone have focused their investments in fewer countries and formed joint ventures or sold their assets in certain countries instead. Even in countries like Australia, Vodafone only own half of their local affiliate and O2 in Slovakia and the Czech Republic are no longer owned by Telefonica.