Can we take a pre-approval from alberta bank to purchase property in Ontario?

It actually depends on the bank in Alberta. Certain banks will only lend within certain areas, so your best bet is to simply ask the bank where you got your pre-approval if they lend outside of Alberta (and specifically in the city you're looking at in Ontario).

As long as the bank that issued the pre-approval is licensed in Ontario, then they should allow you to use it in Onatrio. Be careful that the property you are buying still fits this bank's lending criteria. Should you require additional help, contact a mortgage professional to review it for you and advise. We would be more than happy to help you.

Coming from a broker in Saskatchewan I know that certain lenders will not lend here due to licensing. Ontario being the presence they are likely you will not have that issue but a quick phone call to either the lender you are dealing with or the broker who is working for you will put your mind at rest here.

Depends which Bank it is, just check with them. Anyways, the pre-approval is not a commitment, so I understand your pre-approval will just give you an idea for how much you can be approved, to search houses in this price range

I would be cautious with this, and would suggest that if you are using a nation wide bank that you speak to the mortgage broker who approved your application in Alberta. They will likely refer you to a banker in your new neighbourhood. As a rule, you should ask your realtor to insert the mortgage clause into your agreement of purchase and sale with a minimum 5 working day period. This way you aren't caught in a bad situation.