I would imagine any conversion would be happening at at Bombardier facility since this involves a new type certificate. Don't think TSH has that capability at the STL maintenance facility, plus they have their hands full with TSA and Gojet aircraft.
Just kinda interesting that TSH hasn't announced any kind of delivery plan for the 550s, playing games with the TSA contract, and haven't announced a firm agreement (just a MOU) for the 550s. Also weren't they supposed to negotiate new payrates for the 550? Other interesting rumors floating around about Compass and the removal of the Delta aircraft at Gojet as well. Gonna be an interesting next few months at ole TSH.....
All could come together over the next couple of months, but still interesting nonetheless....