Is it true EX raid passes...

no, are released two days before the event. (this week's was Tuesday.)

no, in New York city. The ex pass will give out two days before the raids. First week Mewtwo raids was on Saturday, second week was on Friday, this week was on Thursday. Each week are different so far.

Mewtwo Raids are still "Field Tests" which is basically Beta. Which means we can't really expect them being regular or anything. Niantic is trying different things out. They've invited different amounts of people in different places, so they're still playing around with things.