I'm not sure this is going to end well for telecom companies. 

It's one thing to have rolled-out miles and miles of cables during the past century and only now discover that the material you used is toxic to residents. That sort of discovery happens every day as new studies are conducted. However it's quite a different thing if you've known this danger for years and didn't do anything to notify people or mitigate the risk. That's negligence and a heaping helping of liability on your hands. 

First things first, mitigate the risk to health and safety and pull out the cables if that's what is needed. That's going to be an expensive proposition -- especially if it means tearing up roads and existing infrastructure to get at the buried cables. 

(This links to an article in The Wall Street Journal. It's supposed to be a free article without needing a subscription. If you try to access the link and it blocks you let me know. I'll send you a PDF of the story.)