I am sure the issue is nothing to do with the high operating costs of the 146. I believe the direct operating costs of the 146 are the same as that of the old Tigers that Bristow used to use on the route, but with 5 times the capacity. Granted now the S92's are allegedly cheaper to operate, but I'm still not sure if the maths works out on an ABZ based operation.
It will be sad to see the 146's leave ABZ, but hopefully the IAC will realise the amazing adaptability of this popular little jet and we will see them return. It is the only jet aircraft that can do the job, the Saab will have payload issues I'm sure as will the Q400. The Dash has been previously evaluated and found not to be able to take the bigger loads out of SCS. I expect the successful tender will still need to keep a hot stand-by aircraft in ABZ, the IAC would not want to risk the integrity of the operation should there be technical or weather problems.