The answer [whether MNTA pays all litigation costs or it is shared with NVS] is unclear and not especially consequential in the overall scheme of things.
As $ paid to litigation I agree that it isn't hugely consequential. But I would suggest it makes a big difference for a variety of related questions:
1) Does NVS get to share in the winnings - should MNTA prevail?
2) Does NVS get to set the goals of the lawsuit - after all NVS isn't hurt as badly percentage-wise by this launch as MNTA. (Figure they went from $1B*0.65(GM)*0.55= $350M in pre-tax profits to $0.5B*0.58(GM)-$0.04B(payments to MNTA)=$250M)