I Recived an email this morning form a reader who noticed the BluePutties in Drydock in Boston.
In the past, Marine Atlantic work has been done in the NovaDock at Halifax shipyards, however I have heard that the Nova Dock is having some sort of issue and is not serviceable. It may also be that the shipyard does not have capacity given its renovations, Final work on the Hero Class, and Ongoing FELEX Work.

Davie in Quebec Has a Drydock large enough, however I belive it is occupied by newbuilds/and or the Louis St Laurent.