From what I read here, every comment on this forum and from ATC was generated from the initial comment from LTD on the day and within this forum.
ATC never says YOU (IB) need to be de-iced, they say BA is concerned.
So, it all goes back to one persons stated observation and opinion. From what I can see here, 13 pages later, LTD is the sole actual eyeball operating witness.
While this is an excellent hypothetical discussion, you may as well delete every reference to any specific operator as there is no actual proof of the alleged incident.
It was the opinion of LTD that IB required deicing. It was the opinion of the IB crew that they did not. You can argue the pros and cons of the resulting decision until the cows come home, but unless you were actually there on the day and saw for yourself, it's all just an exercise in philosophy.
What remains is that what we have here is a difference of opinion between crews of different aircraft. It appears to me that somebody is upset because his opinion, while noted, was disregarded.
PB