|I have no reason to believe that anyone in Congress would want to see my tax return - they re really quite boring, even to me.|
Congress has the legal right to see individual tax returns as part of an investigation and has had that right for over 100 years - this is not something new. What NY is doing is saying that "if you (Congress) need to see a NY resident's tax returns and are meeting resistance in obtaining them, we can provide you with that individual's state tax returns if certain committees request them."
Two points here: The first is that this was CLEARLY targeted at Trump; in fact, that's basically what the original bill did, but the NY Governor said he wouldn't sign such a bill, so the bill as passed doesn't name him - it applies to all NY residents.
Second, the information remains confidential, because the return can only be reviewed in executive session. Yes, Washington does leak like a sieve and the financial information will get out to the media, but the media doesn't publish personal information such as email addresses, telephone #s, SSN numbers, etc. When MSNBC got its hands on a copy of Trump's 1040 for a single year and reported on it last year, it was a redacted copy - all of that stuff was blacked out. No responsible media outlet is going to share that kind of information with the public.