Some real numbers for one of the 605s I fly:
Operating weight with 2 pilots - 27,151lbs
Zero fuel weight with 4 pax and some bags - 28,250lbs
Absolute minimum fuel for flight planned arrival - 2,000lbs. Most pilots are comfortable with 3k+, and they could have been tankering, but this gives us the lowest speeds.
Vref for 30,250lbs at 4500ft elevation - 121kts
For a more likely 32,000 - 126kts
The FCOM says that circling should be done at the Flaps30 speed +10kts. Unfortunately, nowhere is the Flaps30 speed defined. If you take it as being the speed you get from the FLAPS FAIL checklist at Flaps 30, then you get speeds of 138 and 143 respectively. Most operators fly as they have been trained by CAE and FSI and use 150 unless the weight requires more.
So it is theoretically possible to get below 140 if they were light enough, but in practice not likely.
I hadn't spotted the AIM change. They have changed "must" use the higher category minima to "should". In my book, "should" suggests you need quite a good reason not to, and the Boss wanting to get to his summer home doesn't seem good enough, particulary given that even the Cat D protecterd area is quite tight to do any kind of sensible circuit. Everyone who has done the JFK and Memphis circles in the Challenger sim knows that it is rarely a stable approach in anyone's book!
Obviously we need to wait for some facts, but sadly i think that this will demonstrate that pushing things to the limit just because it is legal doesn't mean it is a good idea.