boldsuck
Not disagreeing, but here's some more info about this and a great reply by Proton:
https://www.reddit.com/r/ProtonMail/comments/1930vnh/breaking_news_nsa_style_mass_surveillance/
First, Proton uses end-to-end encryption which makes the encrypted data useless to any intermediary to might sit in the middle and try to capture traffic.
Second, Proton utilizes a second TLS encryption layer for data sent over the wire. TLS covers almost all internet traffic these days (including say emails sent from Proton to Google, which are not end-to-end encrypted, but are TLS encrypted).
Third, as the article mentions, not all cables are tapped, just the "big three" ISPs, which is Swisscom, Sunrise, and Salt. Because Proton controls our own network infrastructure, we act as our own ISP, and are not subjected to the obligations of the big ISPs. So even if we ignore the encryption layers already in place, the main ISP lines does not impact Proton directly because we use our own lines.
Fourth, based on the disclosures of Snowden, we know that the NSA and other intelligence agencies are tapping cables, even if it is against the law (as is likely the case here), so that's why we don't use cloud services like AWS and Proton fully owns and controls all of our servers and network equipment. The benefit of this is that we can put in extra encryption. Our threat model has always assumed all lines are tapped by default (even the ones that we own), so Proton also encrypts sensitive server to server communications within our network, and we also use MACsec to encrypt network traffic between our datacenters, including the traffic that goes over our own lines. We can do this because we control those lines and those networks.
TLDR:
So the short answer to the question of what does this mean for the Proton user is not much, because we already designed Proton assuming all cables are tapped.