Actually, BHP do. and so do a few of the bigger ones. they prefer multi, but will use SE if required. I have carried most of the major players in the resource sector in both SE Piston and SE Turbine
That isn't my experience. BHP/RIO wouldn't even discuss SE turbine and if it wasn't twin they weren't going. You must have some serious contacts to get them into a single because most of the contracts demand twin engine aircraft and pilots with more hours than those getting into regionals.