Still uncertain.
I feel obliged to make the same disclaimers as Tanimbar, although for scientist read engineer - non aero. Nevertheless, I have followed this thread since the day the accident happened, indeed it was the real reason I joined this forum. Mainly because of the almost unheard of bilateral engine 'failure', which from an engineer's point of view is the equivalent of a good 'whodunnit' - better by miles than the Davinci Code. Yes, I know the engines didn't actually fail; failed to respond is a better phrase, but that doesn't get round the fact that both of them did it at the same time.
I have read as much of the linked information about ice carried in fuel and the tests carried out as I could. I have read every linked pronouncement from the AAIB and I have, as I said, read every post in this thread, looking for the little nugget that stops my engineering alarm bells ringing. And the oil heat exchanger on RR Trent option aeroplanes didn't do it for me. I tend to agree with Phil Gollin and Tanimbar, that the case for the heat exchanger is, at best, unproven.
On the other hand, one could - as I often do in my day job - apply the principle of Occam's Razor and say that since this is the simplest explanation, we should not strive too officiously to find another. However, the heat exchanger issue appears to have been addressed and there is very, very little other forensic evidence either way, what if it is not the culprit ..................
Roger.