In the end I would suspect all will pay a share. I say this based on a settlement resulting from the fatal AA accident at Chicago's O'Hare airport years ago. This accident involved a DC-10 where a GE engine broke away from the rear pylon attachment point went over the top of the wing (engineered to do just that), but in the course of this, severed the hydraulic lines that were the main flight control lines located in the leading edge of the wing. The entire DC-10 fleet, all airlines, was grounded until some resolution and checking was completed.
The root cause was identified as AA maintenance removing and installing engines using a forklift truck instead of a special lift provided for this purpose (cost reduction/time reduction decision on their part).
In the end, AA, McDonald Douglas and GE all contributed through their liability insurers to final financial resolution.
You could look at it this way: McDonald Douglas should of had these critical hydraulic lines in the rear area of the wing like the L-1011. GE's engine went over the wing, severing the hydraulic lines and of course AA for their crude engine install/removal practices. Fair? Hard to say.
Turbine D
As critical as the the use of the fork lift (or more so) in AA's shortcut maintenance procedure was their changing out the engine/pylon as a unit, rather than separating the two. This was not recommended by McDonnell Douglas (note the correct spelling) but M-D said it lacked the authority to enforce maintenance procedures.