I agree with Da Grump. This is the "Let's blame the dead firemen" press release.
Years ago I got a tour of Houston FD Station 81. It's the ARFF station for William P. Hobby Airport in southeast Houston on Koonce St. on the south side of the field (HFD Training Academy is about 5 blocks south on Braniff St.). The old ARFF quarters was in Station 36 on the north side and still have the engine and medic. 81's apron leads directly onto the taxiway parallel to Runway 13R. About 150 feet from the station is an alternating black/yellow painted stripe (which you can see on Google Earth). The shift working told us that apparatus was forbidden, under any circumstances, from crossing that hold line until given radio clearance by Hobby Ground Control in the tower.
The Lima Airport has only one runway; 16-34. A second parallel runway is presently under construction to the west. It appears that a new control tower has been built between the two. The new ARFF station is directly adjacent to the tower to the south. With the new station it would seem appropriate to be testing response routes from quarters to any part of the field. However, at present, literally everything- terminals ,hangars, fuel storage, flight line, and parking is on the east side of 16-34. To get to anything you HAVE to cross the runway!
Firefighters that work at airport crash stations (besides being bored) know every square inch of the field, all the relevant rules and SOP's, and the tempo of operations. It's hard for me to believe they didn't know that airliner was a couple of thousand feet up the runway and that they proceeded across it without permission.