They approached twice then went into a hold for 20 mins. This would signify they followed the rules. As mentioned above the fog was very patchy. I was at traffic lights in Cork 20 mins before the accident and couldn't see 100m in front of me. Then all of a sudden I could see over 1km, then back down to about 300m. All in the space of a minute or so.
There are eye-witness reports, therefore the tower had to have seen it, unless the eye-witnesses were closer than the tower, unlikely in Cork.