On a related note, cellphones have been known to upset life support equipment in hospitals. I haven't heard of anyone dying as a result though.
It would appear that any digital equipment is vulnerable to cellphone interference, provided the conditions are just right. As someone already mentioned, it looks like the older analogue cellphones, with higher energy emissions, are the main offenders.
Even if the risk of critical interference is very small, we should still take steps to control it.