If the Coast Guard is involved in escort duty they take this very seriously--especially if they consider it a threat. (How could CG cover all of the Ferry crossings that occur in the Puget Sound to San Juan Islands? Take a lot more resources than are available.
On the other hand, if they thought that there was a serious threat of terrorist attack--that would be met with very serious measures. Lets say that a terrorist had a vessel, full of explosives and was a suicide bomber or a vessel put on auto pilot with the explosives (Ie USS Cole) what would be the procedure?
First, it would be difficult, if not impossible, to fire warning shots over the bow of a boat anywhere in Puget Sound and not hit lawn furniture or worse.
"A shot across the bow," is fired into the water, not toward lawn furniture...or any structures on land.
The procedure in most of the CG interdictions where shots were fired, tend to attempt to disable the outboard motor. i don't know how many of those have occur in the PNW, if any, but in S. Calif. and off Florida there have been a number of incidents where shots were fired eventually disabling the vessel...(But also CG boats have been rammed and personal have been injured.
The ferry could have also just sped up a bit when they first determined that there was a collision track. Nap Time would have then passed behind the ferry and gone on its merry way, possibly hard on some rocks.
A lot easier to speed up a C Dory or other light vessel, than a ferry which is swinging a 10 foot prop with the engine at 900 RPM and already going close to its max speed at 1200 RPM. Lets say that the ferry was going the lower range of its speed at 12 knots, and tried to go up to 18 knots theoretical top speed (which it probably cannot obtain.) This would take a number of minutes. It is probably not possible. The ferry technically was the give way vessel--and should have turned or stopped: Evidence points to the ferry attempting to stop--first by slowing, and eventually starting the second engine.
Close encounters with pleasure boats happen daily with the ferrys. 99% end up with the recreational vessel changing course, stopping or speeding up to avoid collision. Often recreational vessel operators are not aware of the limits of maneuverability of the vessels of the size and type of the Washington State Ferrys.
The ferry skippers have a difficult job even without the foolishness of small recreational boats "challenging " them. The ferry's generally stick to their course and speed. I have seen them on occasion maneuver around a vessel engaged in commercial fishing--and I suspect that they have communicated with the fishing vessel by radio.
It will be very interesting to see the final CG report. Yes, fault will be assigned to both operators. But I suspect that the "protection zone" argument will win. From what I see the operator of Nap Tyme seems to be taking this relatively lightly...Not a good idea when an investigation is on going.