I suspect there may be some accommodation restraints on island, and have heard some type of shuttle from the mainland (such as Karratha) may be in the pipeline, with additional staff housed in camps in Karratha.
I think the BWX strip is Code 3 (146) not Code 4 (E190/738/717) and the ACN of an E190 may exceed the PCN of the movement areas, some sort of concession may be required. Cobham are hence in the box seat as only operators of 146 type.