Line 5 will be hampered by longer dwell times due to the layout and door compromises of using low floor LRVs. I'm not sure how they will handle the issues that come up from the surface section causing disruption to the underground section. Padding at the transition? Disconnect the two segments operationally?
Imagine the service disruptions on the underground portion caused by a vehicle collision on the surface section. They can short turn at the transition, but that may take some time to coordinate.