Just throwing in my 2 cents re: the F100 vs. eJet in regards to cost.
I can think of one route that is operated by both eJet's and F100's under two different mining contracts (Groote), with McArthur River Mine recently awarding a 5 year contract for eJet's to operate their FIFO contract. eJet's also operated The Granites run on behalf of Alliance until they re-opened their Darwin base.
So other than acquisition cost, one could hazard a guess that the operating costs are not significantly more between the two types.
As stated, the prices for first generation eJets is coming down, so that *should* make it a viable replacement.