A blind trust, set up properly, is exactly that. Blind! The trustee, for the duration of the "blind" portion is not in touch with the actual owner in any way form or shape, so doesn't know what will be decide ahead of anyone else.. Moreover, to keep it "blind" from the owner, they normally "switch" the major holdings that would clearly be known to the holder in the first few months months of the blind trust so that, by switching them to something else, the owner would now not know what is in his portfolio. That's how a blind trust is supposed to work. And in Canada, the Ethics Commissioner is supposed to check that all that is being done.
There could be ways to 'figure things out' I would assume if one really, truly wanted to know.
Some of this are assumptions and some are facts. The Trustee must provide quarterly a 'performance' report on the assets being managed.
That could be something as basic as a 1 liner - Jan 1, 2026 - Market Value = XXX$ - March 31, 2026 - Market Value = XXX$ and the Gain/Loss = XXX$ or (+/-) XX.XX%
In that scenario its pretty much impossible to know anything about your holdings.
But, if the quarter statements lists out all the dividends paid each quarter at the individual security holding level, then it could be possible to get a better sense of what is actually held, especially if they list the dividend amount for each security or the date that the dividend was paid on.
A person could take the time to research the date specifically. If it says, dividend paid on March 12, 2026 and the amount was 429.94$, you could run a query on all the securities that paid a dividend on that date and then take the amount of each dividend and divide it onto the amount of 429.94$ until you get a 'round number'. So if Microsoft pays a dividend on Mar 12, 2026 for 4.2994$/share. That dividend divided into 429.94$ equals 100. So, he knows now that he holds 100 shares of Microsoft.
If only the date of the dividend paid is on the quarter performance statement, against March 12, 2026, someone could check to see which securities paid a dividend on that date. It could be 1 security or it could be 35. Reviewing the 35 would bring that number lower (some securities would just not be appropriate based on the 'KYC' criteria.