CSIS only sends a letter by post whether you are in SS or not
CBSA notes are very similar to GCMS notes, Security portion will be redacted. It may show activities such as Security etc, but no additional details
During the PR application time I was under SS..
When I applied for CSIS i ended up with the letter which stated the following
CSIS PPU 005 Security Assessments/Advice - Your Security Screening case is still in progress. The information has been exempted from disclosure by virtue of one or more of sections 21 (as it relates to the efforts of Canada toward detecting, preventing or suppressing subversive or hostile activities), 22(1)(a) and 22(1)(b) of the Act until your case is complete
There is an article on Thestar which highlights the content of the letter when a journalist requested CSIS letter (for non immigration purposes)
https://www.thestar.com/news/privacy-blog/2015/05/what-happens-when-you-request-your-csis-file.html