score:4
According to the website of Park Canada the two categories you mentioned get free access:
There is no mention of any other category that I can find anywhere. However, last year (2018) there were occasions where access was free for anyone:
The free day for each park seems not to happen this year (2019) and I couldn't find any information for Canada Day either, but looking at the link from last year, the press release was from 27 June with Canada Day being on 1 July, so it might still happen.