Clarification from Rexstar.com in the Wood Mackenzie June write-up:
"ExxonMobil would need to agree terms with it's partners to bring the gas into PNG LNG project. This would require it's partners to acquire equity in PRL 15 and agree to a revised project unitisation agreement or accept a tolling fee for Elk/Antelope gas to be processed through PNG LNG.
These options would allow all partners to benefit from expanding the existing project. However, the level of reward available may depend on each partner's abiity to committ to the sizeable investment required to expand the project."
Could well be the time involved in defining the deal involves herding the Gov't and project partners to declare their expansion involvement. XOM doesn't need project partners approval or involvement to move on a 3rd train with E/A gas.