The J41 is being put on the route because there will be no ABZ based J32 from the end of Feb. Fly Be is no factor in the decision process since there would of been a J41 sitting in ABZ for a few hours doing nothing and the ABZ based J32 is going to the new WIC base. However there have been a few J41 flights to BFS recently due to a J32 being filled with good loads.
Look how long Eastern have fought against bmi on the Norwich route and they have not given up. Eastern don't need many bums on seats to make money unlike Fly Be due to their low cost base and the high fares. Expect Eastern to stay on the route - their Chief Exec won't give up without a hard fight! Anyway one of their J41s will be far cheaper than a Fly Be Q400 in leasing costs since BA are still subsidising the J41 leases.