Phil, it comes down to language, no? What does "traffic rolling off the runway" mean? Taking off from the runway, or just landed and is rolling off the runway? Is that a phrase they routinely use in Ireland? (My guess? The 109 pilot thought it was the latter - that an aircraft had landed - and he was looking for an airplane to his right rather than from his left. Why he didn't seek clarification from the controller further is a good question.)
Wouldn't it have been better to say "Pass behind traffic rolling on runway 28...?" Sounds like the controller was using confusing and perhaps non-standard phraseology.
But even if you are correct that the 109 pilots decided to pass behind a big jet that was facing away from them, it surely must have been apparent that said jet was not "rolling off" the runway. He wasn't on the runway at all! Helloooooo, 109 pilot(s)! Heads up, please!
I'm on record as being 110% against mid-field crossings of any kind. I don't like 'em. Mid-field, even at 1,000 feet is no place for *any* aircraft, much less a helicopter. I know it is an accepted practice in Canadia - I don't care. I've had my close-calls. Never again!