Originally Posted by number_6
It sounds like you are changing the first segment in which case you will have to pay any new taxes/fees such as the fuel surcharge for any of the 20 segments. Re-issue after the first segment is flown will not incur this except for any changed routings (at least other fees work this way, not 100% sure if the fuel surcharges don't have special rules).
Thanks for your replies, number_6 and christep.
I was tossing up adding a DRW-BNE segment at the beginning of my OWE. I rang Qantas in Aust, and the CSA, after speaking with his supervisor, said he "believed" upon reissue I would at least have to pay the fuel surchage on my Qantas flights ($15 for International segments, and something like $5.50 for domestic). As he sounded unsure, I then rang Qantas in London, and the CSA, after speaking with her supervisor, told me if I reissued I would have to pay the fuel surcharge and airport tax for the added segment.
I think I'll try ringing on Monday and see what I'm told on my third attempt.