Well that's intriguing.
In the e-mail(s) advising me of the delay/cancellation Aer Lingus had a link to their '261' page where it says:
If you are denied boarding or your flight is cancelled or delayed more than 3 hours on arrival for reasons within control of the airline you may be eligible for a refund, compensation or expenses under EU Regulation 261/2004.
(My bold)
There are links from there to other pages which also limit claims to circumstances within their control.
I reckoned MCO closing because of a hurricane would probably be judged as not within Aer Lingus' control, so didn't try to claim from them.
So I've just had another look at the CAA website*, for UK law (which I thought was still aligned with EU, but maybe not), and seems a bit vague. It reads as though you can claim expenses regardless of the cause, but not compensation if it was out of the airline's control, which would explain why BA paid up for you.
Anyhow, I put in a claim on my insurance 9 days ago, saying I didn't think I could claim from the airline, and the money's gone in my bank today. I'd have thought they'd have bounced it if they thought the airline should pay, but who knows? It was only about £300, so maybe it wasn't worth chasing around.
( * I have it bookmarked having had to brute force money out of BA earlier this year)