Thanks FBinNY.
Yeah I agree with you... something light like TriFlow or SowingMachine/Hair Clippers oil. What would you think of my plan to fit the cables and see what the friction is like before adding any lube? (If there is any grease/oil already applied from the factory, maybe it was injected into the middle of the separate cable lengths???)

It is possible that any 'low friction coating' got applied to the exterior of the inner cables (which are black in colour), instead of being applied to the inner plastic sleeve of the outers. Very hard to tell by looking at the kit (and can't find any Shimano instructions...)