There may be a couple of nuances. Parks Canada is responsible for the conservation and maintenance of the national historic sites that it owns and administers. Other federal departments also own and administer their sites, so they are responsible for the preservation and maintenance of those as well.
When they are federal buildings on national historic sites, there is, under Treasury Board policy and through FHBRO, guidance that's provided for all federal departments on how to maintain their federal heritage buildings.
With respect to your question, I don't know exactly if it's a Parks Canada site in your riding.