With respect, I don't think that's an example of “trust us” when they say courts only give the authorizations after review and therefore this is lawful. You say, "trust us". The question of trust depends on two things: a clear and rigorous legal framework and independent oversight. The courts provide independent oversight.
We have a good starting point with part VI of the Criminal Code. Can it be improved? Probably.
The OPC certainly has particular expertise in privacy to bring to bear, and proceeding with privacy impact assessments is most likely a good idea in the circumstances. There is also the the National Security and Intelligence Review Agency, NSIRA, that plays a role and is also an independent oversight body.
You have at least three institutions in total providing a measure of trust: the courts, the OPC and NSIRA, which are independent from the executive branch.
Your study is about, given the intrusiveness of this technology, whether the safeguards should be improved. It may well be that the answer is yes.