Many, but certainly not all, were produced by Sorel Industries Ltd
of Sorel Quebec.
If you look on the guns often used as gate guards or cenotaph pieces, or in front of legions, you'll likely see stamping and data plates saying SIL indicating it was/is a Cdn made gun.
The southern Ontario based group L:imber Gunners Association operates a fully restored Gun tractor, limber and 25pdr.
(Toronto Oshawa area)
Their website is
http://www.geocities.com/lga25ubique/index.html
Cheers
Marc -editor Convoy Magazine- the world's #1 magazine for CMP and other Canadian military vehicle buffs
http://www.geocities.com/convoymagazine