In this situation, the tower ( ATC ) and the pilots would be in radio contact. ATC would also be in radio contact with the guy in charge of the fire services.At times this guy would assess the fire from the outside as the fire engines are heading towards the plane. If, in his assessment there is no need to evacuate then he would communicate this to ATC , who would then relay the info to the pilots. ATC can also put the pilots in contact with the fire services guy on a seperate frequency for them to arrive at a decision without ATC inputs.
The latest I hear now is that this was the case.