In a previous life (1997/9) I worked in flight calibration - we tested Nav aids. Our testing kit was regularly calibrated. Cellphones were analogue - they are digital nowadays. When calibrating our kit a signal generator that replicates an ILS ground station was connected via a well shielded cable to our "ILS" kit (receiver). If I walked up and down the workshop with my cell phone switched on I could watch the glide slope needle change from full fly up to full fly down, depending on my distance from our kit. I know analogue cell phones can cause interferance to an ILS. I don't know if digital ones can. Also, AC wiring is much more protected today.