Some MBBs come with static shielding, but some don't. Here's how antistatic bags work: "A Faraday cage operates because an external static electrical field causes the electric charges within the cage's conducting material to be distributed such that they cancel the field's effect in the cage's interior. This phenomenon is used, for example, to protect electronic equipment from lightning strikes and electrostatic discharges." And here's how MBBs work: "Two primary moisture barrier technologies are used for bags. Barriers of aluminum foil and aluminized polyester are used where low MVTR is required. Most SMD's are packaged in a metal barrier bag. Thick layers of plastic can also be used to provide limited barrier for very short-term applications." A few mm thick layer of aluminum won't block phone signals. The antistatic bags that computer hardware is sold in may not be strong enough to completely shield phone signals either. I don't know for sure, haven't found any references, but I'd do some research before basing my safety on one of those bags.