Using Freedom of Information (FOI) or Access to Information (ATI) requests to obtain government information can be an extremely effective - and sometimes unavoidable - research tactic.
You need to be aware of issues of time and cost. Some jurisdictions, such as the federal Government of Canada, charge a fee just to file a request. Others do not charge anything for an initial request. Some jurisdictions have a very quick turnaround time, while others - Canada federally, for example - can be quite slow.
There are also rules about which information is available and which information is not. The manner in which you word your request will also affect how quickly and how accurately you get what you want.
Right To Know Canada is the web site of an extremely helpful and comprehensive guide to the web sites of Canada's federal, provincial and territorial Freedom of Information Commissions.