Agree with the tricky part. If I am not mistaken (and this is a pure guess), Telecom and Telefonica are NOT considered a matter of national pride. However, my hunch is that she will go after them. Might not be the next thing because as others are suggesting, there are many other companies she could go after (like Metrogas, she will nationalize that because Axel's got his eyes on it).
Control oil, control electricity and gas, control communications network, etc and you have essentially put yourself in control of the every day lives and wishes of the populace. I am not saying that that is what she wants to do but that is the logical way to go if she wants to get her way today, next year and until the day she dies.
EDIT: I also want to say that the government at this point seems to be going after percieved cash cows. That's another reason I thought they might think of gobbling up phone companies.