"The change that has been made is ... it gives the CEO absolute discretion to make some decisions around marquee players if that is required," Greenberg said.
"At the moment, the CEO has no discretion to make those decisions at all. Under those changes, the CEO has the discretion from 2015."
Asked if those powers could be used to bring Folau back to the code, Greenberg said: "It could be.
"This is designed for a player that would add value to the entire game, not just simply to one club's roster.
"And whatever value a player goes in under the salary cap has to be a market value."
The salary cap will rise to AU$6.55 million next year and increase to AU$7 million in 2017.
Following a comprehensive 10-month review of the cap, NRL chief operating officer Jim Doyle unveiled a number of changes on Wednesday that will take place from next year.
Minor changes were confirmed such as the $200,000 veteran player allowance increasing by up to 50 per cent on a sliding scale with a maximum $250,000 per club in 2015 and $300,000 in 2016.
But the allowance will now apply to players serving six years with a club - not the previous eight years.
Special provisions are made for teams who lose players through terminations and concussion, while transfer fees will be regulated either by including them in the cap or through other mechanisms, but the June 30 transfer window will remain.
Meanwhile, the NRL said the 2015 season would again be launched by the Auckland Nines however the All-Stars clash would return to Suncorp Stadium on February 14 after a 12-month hiatus.
The World Club Challenge will be held in the UK before NRL trials from February 20-22 and the March 5 official kick-off.
The NRL also unveiled the "most significant shake-up to the way the clubs are funded in the game's history".
Clubs will have up to $1 million of a new funding package "at risk" if they don't meet minimum standards.
However, the clubs will also have the opportunity to access a multi-million dollar pool of "incentive payments" if they grow their performance across membership, game-day attendance, merchandise and sponsorship.
It will come into effect from November 1.
- AAP