Yes, it is possible to have an endorsing peer participate in 2 different networks (e.g. a supply chain blockchain n/w and a logistics blockchain n/w) both of which have a separate smart contract. Here, the joint peer will have 2 ledgers from both n/w and can make a transaction in both chains who have different orderer and CA. You have to set up the right read and write transaction permissions for this endorsing peer accordingly in yaml file and have right certificates.
hope this helps
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