Is it true that in an emergency anyone can use a ham radio?
No, it is not true, to the best of my knowledge. A licenced Amateur radio operator (or Ham) has to maintain control of the station, meaning the radio(s) in his/her possession. For example, if my wife or I cannot use our radios during an emergency, our son does not have the right to use the radio in our absence.
The fines and imprisionment terms for using a radio without the operator present and in control can be severe.
As a licenced operator, you have to play by the rules laid out by the FCC, as well as unwritten "gentlemen's agreements" that you learn by becoming a Ham.
During an emergency, a licenced Ham MAY use radios and frequencies that are outside of the bands that they may be licenced for, but only for the duration of the emergency.
Interestingly, a licenced Ham does have the ability to use a police radio to call for help to the agencies' dispatch center, in the event that the officer is not able to use the radio themselves. The police DO NOT have a reciprocal right to use a Ham operators radio, unless the officer is also a licenced Ham for the frequencies covered by the radio.
Getting an amateur radio licence is really not that difficult, nor that expensive. Radios themselves start at about $130.00 for a new unit, and used ones are even cheaper.
But, you do need to have the licence to use that radio, as well as the knowledge to use it properly and safely.
N4MAN