The King Air is a sprightly performer (well, sometimes!) and I know of a 90 that's operated off a private grass strip which is around 800m long.
Would've thought that 6 rotations a day with it might dig up the surface somewhat eventually!
Perhaps it's a cheap way of ploughing - European grants and all that...!
But, for a commercial operation of a King Air you need at least Cat 3 fire cover (yes, 2 if you want to be pedantic!) and the joys of commercial flying would not lend themselves to a private strip which could be closed due waterlogging and has no approach aids (and therefore would require, for Pub Trans, a dispensation for the a/c - and under current JAR regs (which will probably change as I type) that would mean a phone call to the CAA each time. And some money. Funny that.