You can search this Linn message board for a list of counterparties (same banks as on their credit facility).
Keep in mind the counterparties offload the hedge risk to those on the other side of the trade such as airlines. The counterparties on Linn are probably not highly exposed to the change in the hedge value themselves.
As I understand it by using a counter party .Linn does not need to put up margin and does not have to maintain margin if they were to hedge on the NYMEXCL crude oil. Guess this a way to not have your entire bank roll in NY Exch if hedge goes against your poss.I at one time hedged my grain poss. with Chgo Bd of Trade and the margin calls can get big and you find your bank roll in Chgo. Not fun