So basically Tesla can lower FCA's fine arbitrarily low all the way to zero, if FCA agrees to pay it to Tesla.
So both parties benefit from making a deal, and both parties need to cooperate to make a deal. I think Tesla would have a fair expectation of at least 50% of the fines - more if they were the sole (monopoly) source of zero emissions, which Tesla is.
If Tesla played this smart they'd have auctioned it off to
all European carmakers, starting bid at $300m and eliminating the lowest bidder in every round, or something like that. Note that every carmaker would know their
own exposure and bid accordingly, without having to disclose it to competitors or Tesla.
Since the pool is exclusive and non-transferrable the bidders would be in a classic Prisoners Dilemma, highest bidder wins it all.
Wouldn't be surprised if the second to last bidder was PSA ...
BTW., wouldn't be surprised if editors of the Financial Times (owned by FCA owners) would be told to ... not emit as much FUD against Tesla, because now it's in the best interest of FCA as well for Tesla to sell as many zero emissions vehicles in 2019 as possible.
Also note where the news broke first: the Financial Times ...