Hrmm, storm, meet teacup. It's not like reciprocal runway ops for noise abatement late at night are unknown. Brisbane, for example. It's also explicitly discussed in the draft Western Sydney Airport EIS as a means of minimising the number of residents affected by noise late night/early morning. That document seems to manage to talk about the operations strategy without once using the word 'curfew', too.
If it allays the (not unreasonable) concerns of western Sydney households about aircraft noise and helps get Badgerys Creek built, then good on them. As the Ben Sandilands article observes, both sides are falling over themselves to soothe western Sydney electorates before the election. Labor just twigged first to the wedge politics possibilities available in the EIS!