The island has both a (LifeFlight -accessible) helipad -- a dock, with a fast boat always docked there.
Also, I expect the ambulance might have equipment (defibrillator, Oxygen, IVs, etc) not available all over the island -- and, important while waiting for a LifeFlight...
Think about it: makes more sense than equipping an "emergency room" at a fixed location!
TXnMA

(hands in pockets, kicks the sand)...I still like my role play idea....(sniff).....(shuffle)
...for certain VIP's...
...just saying...
an ambulance would be a good way to transport drugged humans to/from the event sites