Where '&' is used, you treat the connection as a single unit. So, in the example you gave, John Doe was one half of the partnership, and Pete and George were the other half.
Perhaps viewing it like a mathematical statement:
Produced = 1 + (1+1).
Where company names are concerned, you see it often...
"Produced by ACME and Roadrunner & Son" where ACME is the first company, and Roadrunner & Son is the second company.
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