Here's the blurb from Amex Plat's website benefits page:
quote Premium Global Assist® Hotline
Whenever you travel, have peace of mind knowing that you have 24/7 medical, legal, financial, and other emergency assistance while traveling more than 100 miles from home. We can direct you to English-speaking medical and legal professionals and arrange for a transfer to a more appropriate medical facility, even if an air ambulance is required. We can also help you with prescription replacements, emergency hotel check-ins and cash access, lost luggage, and more. New additions to this program include assistance with lost or stolen passports, Card cancellation, and emergency Card replacement.5

5. The Premium Global Assist Hotline must arrange all medical and visitor transportation. Because the Premium Global Assist Hotline is an assistance service, we cannot reimburse you for expenses you incur on your own.
unquote

Although not stated, in the past you had to have charged your airline/train tickets with an Amex Plat card in order to be eligible.