JPM may have assumed the duties of operating certain WMB subs but in terms of the property they held/owned. They could not assume those "Successor in Interest" rights since IMO these subs were SPE's. That being the case those assets owned by these SPE's could not be legally sold to JPM. The function performed here by JPM would be in a custodial capacity.
Successor in Interest Law and Legal Definition. The term successor in interest means a successor to another's interest in property, especially a successor in ownership of a business that is carried on and controlled substantially as it was before the transfer.
Escrow Returns: $2-$10 Billion....75%/25% to the End