A Vehicle chasing a Bird or Fox or Moose around the airport has to ask for clearance every time he crosses a Holding Point Yellow Line.
Did you give him a blanket clearance to pursue said fox/dog?
The Eurocontrol training zone has a bit on runway incursions and holding lines.
Suppose I give a vehicle an instruction
"...... procreed on RWY XX/XX and listen out" instead of "...... procreed on RWY XX/XX and listen out next report RWY vacated on TXY ...".
I observe the patrol to its conclusion where the driver leaves the vehicle and enters the fire station.
There has been no further communication between me and the vehicle.
Now is the RWY clear?