Inmarsat are not the enemy here - they're the only organization that's provided any useful information whatsoever to the search.
Inmarsat have gone far beyond where they need to go in providing the service they were paid for. They've put considerable time and effort into new work to help the investigators, and located the wreckage to within a million square miles. I don't see why a reasonable court would demand they hand over their private records, even to someone with standing to ask for them.
Their reputation is now at risk from all the doubts flying around. The best way to avoid that would seem to be to publish their 12-16 data points for the arcs and doppler speeds, with a summary of the conclusions that set off the Australian snipe hunt. Duncan Steel can redo his sums, which might focus the snipe hunt, and the more reasonable conspiracists will be satisfied.