I really think the deal that they are working on is an exit strategy with American. Envoy is already trying to grow their 175 fleet by one and one third by the middle of 2020. The 20 compass birds (as they call them) would make that a one and two thirds fleet expansion in a year.
If I were American I'd be feeling a little burned by Delta. Could Republic hand attrition, and 50 planes over the next year? (Delta and American)
American could pay compass a premium to keep flying them until 2021 when they can be shifted over when envoy factory new deliveries are complete.