A slight pedant but the city museum is the old CP station. Until they built their new (ish) station, the ONR used the CN station on 2nd Ave.
Spending money to restore either of them would be s pretty tough sell for a publicly funded entity. There is a
private group trying to raise money to restore 503 although I don't know if they are making any progress. No clue what it would cost other than guessing - a lot.
Actually operating an artifact is matter of much debate in the museum world with most landing on the side of 'not'. The Canadian Warplane Heritage Museum, in spite of its name, is not considered a museum by the larger history and heritage community. The operating costs regulatory hurdles and liability insurance of operating a restored locomotive would be off the dial, that's why most heritage entities that operate anything are private.
No museum has a lot of money unless they have benefactors with deep pockets. The city museum is no different. It gets to spend as much money as council give it, and a municipal council is always cognizant of property taxes. Even if one of them was gifted to them fully restored, it then becomes a matter of paying for site prep, movement, insurance, and on and on. They were pretty much guilted into taking the Dionne homestead when they really didn't want it.