OK, I got what I think is a reliable account of things. This comes from someone well connected to police/fire/coast guard who were directly involved with the incident.
As discussed, there are 4 deep water LNG ports off Salem/Boston/Gloucester just over the line into federal waters. There are well marked keep out zones around them, they are published in the Coast Pilot, and show clearly on any chart less than about 10 years old. There also is a work boat that, as best I can tell, lives out there and warns people off if they get too close. All the gear for the LNG stations is well below the surface, and the off-load attachment port only comes up to connect to a ship for off-loading. In the absence of an LNG tanker, the only thing at or near the surface is a lighted buoy marking the filling turret.
The BHC boat not only ventured into the keep-out zone, but managed to hit a bulls eye on the market buoy and get snagged by it. This was a colossal screw up by the captain, and is why they paid out big bucks to the passengers, and why two CG cutters stayed with them through the night. Normally the CG wouldn't even come out for a stuck boat, let alone stay with it. I expect passengers were asked to sign a "receipt" for the $500 which releases BHC of liability, but that's just conjecture of what any half-wit corporate lawyer would do.