John,
Sorry I can't understand your point, please could you amplify why you would certainly evacuate? Please bear in mind the OP might be flying an aircraft where the second engine master off may occur as an ECAM action as part of the first engine fire. This changes in later FWC revisions so he may not have taken a decision to evacuate when the second engine is shutdown.
OP - From FCOM -
ENG FIRE pushbutton remains on, as long as fire detected
Exactly what sonicbum said...