I can tell you for sure that you can't get from EWR to SYD/AKL via Europe on a single reward ticket. I traded emails with Scott and his explanation was that EWR-LHR-BKK-SYD was "Too indirect". I pointed out that TPA-SIN(BKK)-SYD was even more miles, but chose not to push the issue. The only explanation I sought of half-bought (from FT) was that this would be 4 continent trip.
You can go LHR-BKK(SIN)-SYD but you need to buy a separate revenue ticket to LHR (or another award ticket, and now it is getting very expensive). Still, the BC tickets are out there, although by somewhat circuitous routes. I am looking a few right now, but am not sure how to convince my wife that it makes sense to go (on the return) AKL-SYD-SIN-NRT-SFO-EWR.