Hello from nearly seven years later
I went looking for the film (which I saw in the cinema at release) when someone on another forum reminded me of it - only to discover that it's not available on digital anywhere, and this 2010 Blu-ray appears to be out of print. However I found a copy at Amazon AU and ordered it, so I'll be back to report on how it looks.
I'd imagine they would've just had to go with whatever 1080p transfer existed, and the label that put it out (Dendy, which had the rights for Icon at the time) was known to sometimes use 25fps masters made for television.