According to city archives, Montreal built 23 public baths around the turn of the century. Most of these are located in the east and southeast which were traditionally industrial areas with a real need for a public hygiene system. I couldn't find all of them, a few are abandoned and many have been repurposed. The ones that now serve a different function can obviously be visited, though not in a guided-tour or tourist-informational sense. Some people venture into the abandoned ones, though that's generally not recommended.
Sadly, it seems none are used as public baths anymore, although the city has an archive of old photographs about what kind of events took place there.
If one is interested in architecture however, they're great to visit even just from the outside and many feature turn of the century or Art Deco design.
Here's a few, I'll update this list with more information if/when I visit them.
1- Bain Maisonneuve: probably the best known and best preserved public bath house in the city, built around 1914 in Beaux Arts style. Also known as Bain Morgan, it's now a public swimming pool.
1875 Blvd Morgan, Hochelaga-Maisonneuve
2- Bain Émard: also built around 1914, seems to have been converted to a public swimming pool house. The only one I found to have its own entry on the archives page of the city.
6071 rue Laurendeau, Ville-Émard
3- Bain Quintal: built around 1933 in Art Deco style, also a public swimming pool.
1550 rue Dufresne, Hochelaga-Maisonneuve
4- Bain Saint-Michel: one of the rare public baths west of Hochelaga, built around 1910. Has been converted to a theatre, though up until recently there was public work nearby preventing easy access.
5300 rue Saint-Dominique, Mile End
5- Bain Hogan: built in 1931. I couldn't find any record of it on the city website, probably abandoned.
2188 rue Wellington, Pointe Saint-Charles
6- Bain Schubert: built in 1932, another one in the Plateau Mont-Royal borough, it's now a swimming pool.
3950, Blvd Saint-Laurent, Plateau Mont-Royal
7- Bain Mathieu: built in 1931, possibly abandoned. This article says it was converted to a party venue.
2915 rue Ontario East, Hochelaga-Maisonneuve
8- Bain Hushion: built in 1914, supposedly abandoned too.
757 rue des Seigneurs, Saint-Henri
9- Bain Rosemont: built in 1951, possibly one of the last to be built in the city, is now a public swimming pool.
6101 8ème Avenue, Rosemont