I don't see why they don't do like the rest of the airline world and just order a new fleet of Q400 on lease reducing maintenance costs and unexpected downtime costs for unreliable hardware.
Lease costs are low because the lease company retains title and can repo the plane when/if the leasee defaults. They're not even in some remote location where it isn't easy to repo a plane if need be.
They must be tied up in knots with their existing lease agreements.