If you haven’t already thrown your phone/tablet/computer across the room and cursed my existence yet, thanks for giving this idea a chance.
It’s definitely not unheard of for long-time rivals to occasionally make deals with each other. The Cubs and White Sox have made deals over the years swapping players like Sammy Sosa, Ron Santo, and most recently Jose Quintana.
If you don’t remember, the Cubs and Cards have done deals themselves in the past. Going all the way back to 1900 when the Chicago Orphans purchased the contract of Cupid Childs from the Cardinals.