Photo Of The Day

I'm pretty sure that hippy wasn't in Scotland at the time of the incident, though.

Ha! repped.

Normal for Scotland, and therefore normal for a wind farm sited on top of a hill in Scotland
Unless you have more data than I already alluded to, the recent storm hit a ~15-year high for recorded gusts, around 8mph below the record.
Obviously one would hack whatever controller was in play, I just used Stuxnet as a known example.
What follows is speculation from somebody without your detailed knowledge of the subject, so feel free to mark my work:
The fact that it caught fire, rather than breaking up as other turbines have in high winds, suggests some possible failure modes and over-speed wouldn't be the first one on my list - you surely couldn't generate enough heat in even a failed shaft bearing. I would expect there to be very robust last-resort over-current protection, so an electrical fault, while possible, ought to be an unlikely candidate for fire starting. That's why I settled on the failure to coordinate blade feathering and turbine braking. It would be feasible to mechanically interlock these systems to prevent braking of a turbine set to a power-producing pitch, but I'm not sure that one would do so as a failure in the linkage could hold off the brake even when feathered, which seems like a higher risk than the one you're trying to mitigate. If the feather/brake interlock is implemented in software, that provides a potential attack vector/catastrophic bug.

Wind farms are designed for a 25 year life (often only installed for 20 years due to planning restrictions though). They are designed to withstand the 100yr max 3s gust, modelled for the particular hill they are on, which they may have just been hit by. The recent weather is still not considered 'normal' though. (I do have recorded wind data, having modelled around 150 wind farm sites in Scotland). Note - this is only one turbine, there are many many more that safely weathered the storm.

There are mechanical fail-safes all over the place in wind turbines (including the pitch and brake). They should over-ride any software control, a bug wouldn't be able to be introduced to the turbine control system other than extremely maliciously, a bit pointless as you'd need to have an extreme weather event at the same time to do any damage.

Your thoughts above are along the right lines - the fire (which was short lived) was the fibreglass nacelle housing, I would expect it was an electrical fault, or lightning. An electrical fault would be triggered by a failure of the pitch and/or brake causing the generator to overload if stil grid connected (which would need a failure on the breakers as well).