This report from Steve Lewis, a Herald reporter who was investigating the issue, contains a telling paragraph:-
Grech told me he could tell me everything about the whole affair. Well regarded around Canberra as a diligent bureaucrat, Grech had been given my phone number by Turnbull.
Not evidence that the Opposition was behind it; god knows they have a vested interest in discrediting Rudd and Swan, but it does make me wonder why on earth someone as highly-placed in the public service would fabricate something which could have brought down the Labor government, unless they had expectations of being rewarded somehow, by someone in a position to see to such a reward.
*shrug* I don't know what the real story behind this is, but I do hope we find out.