That depends entirely on the voltage in the wires. A proper high voltage line could draw an arc to the wheel and chassis if they get close enough (less than a meter can be enough). The people in the cabin should still be protected by the Faraday effect. But anything outside that cage or close by may be effected - it's almost impossible to predict which way the currents would flow.

Not necessarily.

Searching online, you find varying opinions, with little evidence. Eg most are insulated; most aren't; it's an issue of not being insulated enough to prevent arcing; in case of fault, insulation may burn away due to high current etc. I'm not sure what to believe.

Isn't an "apron" in this case an overhead structure? They might have been worried about the power lines touching the top or sides of the truck, or getting tangled and making the situation worse.

The apron is just the asphalt ("tarmac" for the British) area in front of the station.

Apron in this case is more or less the driveway, I believe. From the photos (and expectations from living in Santa Clara county for several years), there is no overhead structure outside fire department buildings.

From what I can tell, the fire engines couldn't go out the front, because the wires were hanging down over their driveway and they didn't want to strike them on their way out.