In terms of listing of properties Ontario and Alberta and New Brunswick are similiar as they are constantly updated. BC Property listings come out I believe twice a year fall and spring along with other provinces.
How large is the tax sale property market in Alberta compared to Ontario? Well in terms of the number of properties 1/4 or less. In terms of population ratios to tax sale properties, they are about even.
In terms of buying property in other provinces.. Remember if you don't visit the property, have photos of the property you are not going to be informed in all aspects of the property and might invest in a property you shouldn't. Many things can go wrong and its not as easy as bidding on a property at tax sale, winning the property than selling it through a proxy in another province. If you can't visit the property you can't rebuild parts of a home that need fixing, or evict people living on the property or anything else that could complicate issues.
I would suggest unless you have contacts or family members in those provinces to be wary of randomly bidding on properties in distance provinces. It would be similiar to someone in the Alberta randomly bidding on an Ontario property and finding out those great London Ontario properties last October were contaminated and unfit for human life