The -17 engine is the commercial (type certificated) version of the -703 which is not type certificated. The differences are relatively minor and I believe a 703 can be made a -17 by complying with some service bulletins.
I have to say that in the US where we have public agencies flying restricted catagory or non-certificated Hueys hoisting the public, I am surprised that none of the civil operators have pushed the point that you cannot do any class D loads(non-jettison-able) unless you have a Catagory A Helicopter so why do public use agencies get to do that? The move to twin engine is an expensive one and near as I can tell cost is the ONLY reason to not be using twins for this type of work. An engine failure with people on the hook simply cannot end well unless all are very fortunate.