On the first part of your question, on how will I get information from the CRA, knowing how to ask the question and what to ask for is often key. CRA is by its very nature a risk averse institution. They have the privacy of Canadians' tax information at the top of their concerns. Anything that could be remotely seen as infringing the privacy legislation, they take with great caution.
That means even what we call “residual disclosure” in the parlance of economists and data geeks. For example, even if they remove the name, address, postal code and social insurance number, there is a possibility that somebody could link one tax record to a particular individual based on the characteristics of that tax record. Tax records include lots of information.
They are very worried about residual disclosure. That's why they will want to aggregate as much as possible the data that they send. But there are ways to ask questions and to ask for data that do not risk residual disclosure. In my former capacity, I worked with the previous PBO to ensure that he was able to get access to the information that he needed by directing him to what was feasible within the confines of the law. The request for information was totally legitimate, but the level of detail was probably too fine for the comfort of the CRA.
By aggregating the tax records that he was looking for, that's how it was possible to come to an agreement that was satisfactory for both parties.