its really easy to hide cellphone from towers, the problem is that then it become a useless brick or a desktop-like mini device to connect to usb tethering to connect to the internet... nothing that fulfill the feature of a smartphone without being tracked... and thats because smartphones are tracking devices.
Discussion
I've been using a faraday bag for my phone everyday for over the last year. I can say it can still be used if you download the content first and you have a pair of wired earphones/headphones. The cell connections will be blocked and you'll still be able to consume content. There are also bags that have a small opening to access the screen. Altough I think this defeats the purpose of the farday cage.