It wouldn't surprise me if Russia or other nations have tapped into those lines already and have done for years undetected as a surveillance method, there is no tampering alerts or anything on these lines so who's to say its not already done, the amount of data being transferred would be enormous.
I mean, I can't be the only one who's played with Cain & Abel, it takes minutes to sniff packets for information on a network. Just think what a government could do that has far more resources than a free bit of software and a little bit of knowledge, tapped into the wider web of an entire nation.
Cutting then I would imagine would be a last resort "if" they could potentially tap in, would be far more valuable active.