I do think that there should have been an effort to contact the DCA fire department by tracon land line. the fire fighters could have raced over to the tower to investigate.
I'll bet that tracon doesn't even have their phone number...depending upon tower to do the contacting in other sorts of emergencies.
regarding vehicle on the runway...the runway is usually served by tower freq and it should be on tower freq...indeed, with one controller at this time of night, the two positions and freqs (tower and ground) should have been combined into tower only.