|amenity = emergency phone|
|Using this tag is discouraged, use emergency=phone instead.|
|Used on these elements|
|Tools for this tag|
This feature has been labeled as deprecated. The recommended replacement is: emergency=phone.|
The reason is documented in Deprecated features. You are still free to continue to use or interpret this tag as you see fit since OpenStreetMap does not have “banned features”. Under no circumstances should you (semi-)automatically change “deprecated” tags to something else in the database on a large scale without conforming to the Automated Edits code of conduct. Each of these changes would be reverted.
...has always been the label on this wiki page, however...
This amenity=emergency_phone tag was proposed (Proposed features/emergency phone) in 2008 and adopted by mappers to some extent. It was added to the 'standard' rendering (while emergency=phone is not currently rendered) In the discussion of this rendering issue questions are being asked about automated edits skewing the stats. Meanwhile JOSM validator comes down heavily in favour of the emergency=phone and will auto-fix to it.