Not sure about the situation in Switzerland, but it might not be the same network. I use a somewhat more expensive provider (20 euro topup/month for 10GB data, unlimited everything else), because the one that does it for 10 euro is using a different tower network with poorer coverage and much higher congestion (at least in the areas I'm concerned with).

It's not the same network. There are three providers in Switzerland. From my own experience the most expensive one (Swisscom, by whom this article is) has much better coverage in the mountaineous areas compared to the other two.