T-Mobile has absolutely nothing about this update on their website, "ask T-Mobile" is a waste of words. The call center isn't going to have more information than the website does. It's a legitimate question, Samsung sent the update to T-Mobile, and Samsung makes sure T-Mobile implements the update correctly. T-Mobile isn't going to release anything about this update until Samsung says they can.
Probably within 72 hours of it appearing on their website. Since we have a carrier locked device, we can expect some delay. Last time around they were actually pretty quick so I would not worry too much.